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Gemstone Reference
| A - B | C - F | G - L |
| M - P | Q - S | T - Z |
African Turquoise (hardness 7)
This stone is not a Turquoise but a Jasper. It has similar colour and pattern to Turquoise and that's where the name came from.
Agate (Chalcedony) (hardness 7)
Agate shows a characteristic banding that distinguishes it from other kinds of Chalcedony (which is the compact, microcrystalline variety of Quartz). A lot of Agate gemstones are dyed to quite bright colours at times. A popular form of Agate is Moss Agate which is translucent and colourless with dark, moss- or treelike inclusions.
Amazonite is a form of alkali feldspar, a semi-opaque, blue-green variety, named after the Amazon River. It's striking colour is due to the presence of lead. It is limited in occurrence and fractures easily but still used for jewellery due to the bright colour.
Amber belongs to the group of organic gemstones. It is mostly golden yellow to orange in colour, but green, red, violet and black Amber has been found as well.
Pressed Amber
To create pressed Amber, little Amber pieces are mixed with Copal and pressed together under heat. Copal is a natural resin - just like Amber - but it is only 100 - 1000 years old instead of 1 000 000 years as is natural Amber.
Amethyst is a violet variety of quartz often used in jewelry. The name comes from the Ancient Greek a- ("not") and methustos ("intoxicated"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.
Quartz crystals that are part Citrine and part Amethyst are called Ametrine.
Andalusite (Aluminium Silicate) (hardness 7.5)
Andalusite varies in colour from a pale yellowish brown to a dark bottle green, dark brown or greenish red.
Apatite (Calcium Phosphate) (hardness 5)
Apatite is rather soft and therefore rarely found in a faceted form. Colours range from yellow to green with bright and paler tropical blue. Gemstones are very brittle so careful handling is required.
Apatite is one of few minerals that are produced and used by biological micro-environmental systems. Hydroxylapatite is the major component of tooth enamel. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material.
In the United States, Apatite is often used to fertilize tobacco. It partially starves the plant of nitrogen, which gives American cigarettes a different taste from those of other countries.
Aquamarine, Beryl (Beryllium aluminum silicate (hardness 7.5)
The favourite colour of Aquamarine used to be 'sea green', back in the 19th century. These days, the most valued colours are sky blue and dark blue. Almost all Auqamarine on the market has been heat treted to enhance its colour.
Aragonite (Calcium Carbonate) (hardness 3.5)
Aragonite is usually transarent or translucent and white. Impurities may cause shades of yellow, blue, pink or green.
Astrophylite (also Astrophyllite) is a very rare, brown to golden-yellow mineral. It is heavy, soft and fragile.
Aventurine is a form of Quartz which contains inclusions of small crystals that reflect light and give a range of colours.
Aventurine Feldspar, Sunstone, Oligoclase (sodium calcium aluminosilicate) (hardness 6)
Sunstone has reflective inclusions of red, orange, or green platy crystals, which give it a metallic glitter.
Azurite (copper hydroxycarbonate) (hardness 3.5)
Azurite is an azure blue copper mineral, usually found in massive form intergrown with Malachite.
Blackstone is a natural stone, dyed black. Hardness varies depending on material used.
Bloodstone, Heliotrope, Chalcedony (hardness 7)
Bloodstone is an opaque green, spotted with red, variety of Chalcedony.
In the Middle Ages, Bloodstone was attributed with special powers, as the spots were thought to be the blood of Jesus Christ.
Bone beads seem to have first come into existence around 2200 BC in Ancient Egypt. They were used for trade, in place of money, as decoration and of course as adornment. Bone beads these days are made from a range of animal bones, depending on country of origin.
Bronzite is the greenish brown variety of a series of minerals which includes Hypersthene and enstatite. Bronzite is dark, slightly brittle with a bronzelike luster, but is not seen very often in jewellery.
Calcite (calcium carbonate) (hardness 3)
Calcite is the principal component of limestones and marbles. It is only faceted for collectors, but beads are occasionally available.
Carnelian, Chalcedony (silicon dioxide) (hardness 7)
Carnelian is the translucent, reddish orange variety of Chalcedony. The various shades of red are due to the presence of iron oxide.
Chalcedony (silicon dioxide) (hardness 7)
Chalcedony is the compact, microcrystalline variety of Quartz. It has been used for jewellery for thousands of years. Dyeing Chalcedony has been popular since the middle ages. These days, you see dyed Chalcedony more often than non dyed gemstones. In fact, good quality, holly blue natural colour Chalcedony (mostly mined in Turkey) is one of the highest priced varieties.
Charoite is a strong, translucent lavender to purple in color, reminding some of a granite or marble with its pearly, swirling luster. However, it is a discrete mineral rather than a rock. Charoite is a rare mineral, named for the Chara River and found only in the Sakha Republic, Siberia, Russia.
Chrome Diopside (Calcium Magnesium Silicate) (hardness 5.5)
This is the very bright green variety of Diopside (left photo), coloured by chromium.
Chrysoberyl Cat's Eye (beryllium aluminum oxide) (hardness 8.5)
The Chrysoberyl group includes Chrysoberyl, Chrysoberyl Cat's Eye and Alexandrite.
Chrysoberyl occurs in a range of colours, from green, greenish yellow, and yellow to brown. It is hard and durable. Due to canal- or featherlike fluid inclusions or needlelike inclusions of rutile, Cat's Eye has a near-white line running across a yellowish gray stone. The most highly prized Cat's Eye colour is a light golden brown, often with a shadow that gives a light and dark, 'milk and honey' effect.
The very rare and valuable Alexandrite changes colour from green in daylight to red, mauve or brown under incandescent light.
Chrysocolla (hydrated copper silicate) (hardness 2.5 - 3.5)
Chrysocolla has an attractive blue-green colour and is a minor ore of copper. Because of its light color, it is sometimes confused with turquoise. Commonly it occurs only as pourous crusts unsuitable for gem use, but high quality, gem grade chrysocolla can be translucent and is highly prized.
Chrysoprase (silicon dioxide) (hardness 7)
Chrysoprase is the translucent, apple green variety of Chalcedony. The colour derived from the presence of nickel.
Citrine (silcon dioxide) (hardness 7)
Citrine is the yellow or golden yellow variety of Quartz. The yellow colour is due to the presence of iron. Natural Citrine is usually pale yellow and rather rare. Most Citrine on the market is heat-treated Amethyst. Very pale yellow Quartz, without the golden tone, is called Lemon Quartz.
Coral (calcium carbonate) (hardness 3)
Coral is made up of the skeletal remains of marine animals called coral polyps. These tiny creatures live in colonies that form branching structures as they grow, eventually forming Coral reefs and atolls. The surface of these coral ‘branches' has a distinctive pattern made by the original animals - either striped or like wood grain. Coral is soft, it has a hardness on the Moh's scale of only 3.
Most Corals - red, pink, white and blue varieties - are made of calcium carbonate; black and golden Corals are made of a hornlike substance called conchiolin.
Since the coral reefs have been extensively over-harvested and under thread through environmental changes, harvesting is very restricted and Coral has become exceptionally expensive.
Most Coral, especially the cheap varieties are not precious coral, but sponge or branch coral and is in most cases dyed to create the bright colour. Coral is also widely imitated by porcelain, stained bone, glass, plastic or rubber and gypsum mixtures.
Cubic Zirconia (zirconium dioxide) (hardness 8)
Cubix Zirconia is the cubic crystalline form of zirconium dioxide (ZrO2). The synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconium silicate.
Denim Lapis Lazuli (hardness 5-5.5)
Denim Lapis Lazuli is a rock, not a mineral: whereas a mineral has only one constituent, lapis lazuli is formed from more than one mineral.
The main component of lapis lazuli is lazurite (25% to 40%), a feldspathoid silicate mineral composed of sodium, aluminium, silicon, oxygen, sulfur, and chloride. Denim lapis lazuli also contains a considerable amount of calcite (white).Compared to Lapis Lazuli, the Denim variety contains more white Calcite and less (higher prized) blue constituents and pyrite. It is therefore cheaper.
Diamond (carbon) (hardness 10)
Diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face centered cubic crystal structure called a diamond lattice. Diamond is the second most stable form of carbon, after graphite; however, the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is specifically renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material synthesized so far. Those properties determine the major industrial application of diamond in cutting and polishing tools.
Diamond has remarkable optical characteristics. Because of its extremely rigid lattice, it can be contaminated by only few types of impurities, such as boron and nitrogen. Combined with the wide transparency, this results in clear, colorless appearance of most natural diamonds. Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green, purple, pink, orange or red. Diamond also has relatively high optical dispersion, that is ability to disperse light of different colors, which results in its characteristic luster. Excellent optical and mechanical properties, combined with efficient marketing, make diamond the most popular gemstone.
Most natural diamonds are formed at high-pressure high-temperature conditions existing at depths of 140 km to 190 km in the Earth mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years, which respectively corresponds to roughly 25% and 75% of the age of the Earth. Diamonds are brought close to the Earth surface through deep volcanic eruptions by a magma, which cools into igneous rocks known as kimberlites and lamproites. Diamonds can also be produced synthetically in a high-pressure high-temperature process which approximately simulates the conditions in the Earth mantle. An alternative, and completely different growth technique is chemical vapor deposition. Several non-diamond materials, which include cubic zirconia and silicon carbide and are often called diamond simulants, resemble diamond in appearance and many properties. Special gemological techniques have been specially developed to distinguish natural and synthetic diamonds and diamond simulants.
4Cs diamond buying advice
Diamonds are available in varying colours, sizes and qualities. They naturally occur in colours ranging from very clear fine whites to pinks, bright yellows, greens and browns. The majority of diamonds used in jewellery today are white diamonds.
The value of a white diamond is determined by what are commonly referred to as the 4Cs. The 4Cs are the Diamond's Cut, Colour, Clarity and Carat. Each of the 4Cs are important and the most valuable Diamonds are those that possess the best of all four measurements.
Clarity
Clarity is the term used to describe the size and number of inclusions in a diamond. Almost all diamonds contain minute traces of non-crystallised carbon, the element from which they were born. These inclusions are nature's finger print and make every diamond quite unique. Most are not discernible to the naked eye and require magnification to become apparent.
Large inclusions interfere with the dispersion of light and therefore the diamond's brilliance. The larger or more numerous the inclusions the less valuable the diamond. The fewer the inclusions, the rarer the stone. Each diamond will have its own unique inclusions in various positions within the diamond. VVs, Vs and Si inclusions are not visible to the naked eye, they are only visible through magnification.
Colour
While many diamonds appear colourless, or white, they may actually have subtle yellow or brown tones that can be detected when comparing diamonds side by side. Diamonds were formed under intense heat and pressure, and traces of other elements may have been incorporated into their atomic structure accounting for the variances in colour.
Diamond colour grades start at D and continue through the alphabet. Truly colourless stones, graded D, are extremely rare and very valuable. The closer a diamond is to being colourless, the rarer and more valuable it is.
The colour of a diamond is graded with the diamond upside down before it is set in a mounting. The first three colours D, E, F are often called collection colour. The subtle changes in collection colour are so minute that it is difficult to identify them in the smaller sizes.
>Although the presence of colour makes a diamond less rare and valuable, some diamonds come out of the ground in vivid "fancy" colours - well defined reds, blues, pinks, greens, and bright yellows. These are highly prized and extremely rare.
Carat
The weight of a diamond is measured in carats. One carat is divided into 100 "points" so that a diamond of 25 points is described as a quarter of a carat or 0.25 carats.
The larger the diamond (and therefore the rarer) the more expensive per carat it will be. For example, a 1ct diamond costs much more than two 1/2ct diamonds and one 30 point diamond costs much more than 30 one point diamonds.
The Carat measurement of a diamond is actually a measurement of the Diamond's weight rather than its size or diameter. This is important to remember as depending upon the proportions of the Cut of the diamond, some diamonds may appear to have a larger top surface area ("table") than an ideal cut diamond but the diamonds may be of the same carat weight. Diamonds are sometimes cut in shallow proportions (see below) to make a diamond look bigger but this sacrifices the brilliance and life of the diamond and make them less valuable. See the information about Cut below for further details.
Do not confuse carat with karat. Carat refers to stone weight while karat refers to fineness of gold.
The table shows the approx. realation between the diameter and the carat weight of a round, modern brilliant cut diamond.
| size in mm | weight in pints (100pts=1carat) |
| 1.0 | 0.005 or 1/2 pt |
| 1.4 | 0.01 |
| 1.7 | 0.02 |
| 2.4 | 0.05 |
| 3.0 | 0.10 |
| 3.4 | 0.15 |
| 3.8 | 0.20 |
| 4.1 | 0.25 or 1/4 carat |
| 5.2 | 0.50 or 1/2 carat |
| 5.8 | 0.75 or 3/4 carat |
| 6.5 | 1.0 or 1 carat |
Cut
While nature determines a diamond's colour, clarity, and carat weight, the hand of a master craftsman is needed to release its fire and beauty. The cut gives each diamond its unique sparkle and brilliance by allowing the maximum amount of light to enter and reflect back out of the diamond.
Diamonds may be cut in different shapes with the most common shapes being round (brilliant cut) and what are referred to as fancy cut diamonds including marquise, oval, pear shape, baguette and princess (square)cuts.
Ideal proportions
When a diamond is cut to ideal proportions, light is reflected from one facet to another and then dispersed through the top of the stone. The light refracted externally will amplify and disperse the refracted light from within to provide a myriad of colours and an even concentration of light, brilliance and lustre. A skilful Diamond Cutter can unlock an incomparable natural beauty by accurately arranging each facet to maximise the amount of light returned to the eye of the observer.
To find the best Diamond that fits within your price range it essentially comes down to a compromise between the 4Cs and your consideration of which factors are most important to you. You may choose a larger lower colour diamond or prefer a smaller high colour, cut and clarity diamond.
Dumortierite is a fibrous aluminium boro-silicate mineral. It occurs in blue, greenish-blue, violet-blue, pale blue and red. It is not seen very often.
Emerald (beryl) (hardness 7.5 - 8)
Emerald is colored green by trace amounts of chromium and sometimes vanadium. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor. The word "emerald" comes from Latin smaragdus meaning "emerald" or "green".
Fluorite (calcium fluoride) (hardness 4)
Fluorite comes in a wide range of colors and has subsequently been dubbed "the most colorful mineral in the world". The most common colors are purple, blue, green, yellow, or clear. Less common are pink, red, white, brown, black, and nearly every shade in between. Color zoning or banding is commonly present. The color of the fluorite is determined by factors including impurities, exposure to radiation, and the size of the color centers.
The material, Fossil Beads are made of, has been formed by the skeletons of countless tiny sea creatures. This materil is especially cut to reveal unusual and interesting surface features and finally dyed to a bold and bright colour.
French Jet (hardness under 5.5)
French Jet is not Jet at all. It is black glass, used to resemble real Jet.
Garnet (neosilicate) (hardness 6.0 - 7.5)
The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. Six common species of garnet are recognized based on their chemical composition. They are pyrope, almandine, spessartine, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite.
Gaspeite (nickel magnesium iron carbonate) (hardness 4.5 - 5)
Gaspeite is considered a rare mineral, being found in only a few localities, but it is becoming a popular mineral in the semi-precious stone markets. Gaspeite's light green, almost apple green color is quite unique and not hard to mistake.
Lampwork is a term used to describe glass beads made by melting glass with a torch and wrapping it around a metal rod. The term "lampwork" was used many, many years ago when people used to blow air through oil lamps to melt the glass.
Lampwork beads are often kiln-annealed so they won't break as easily.
Annealing is the process of slowly cooling beads in a temperature controlled kiln (oven) so that the glass molecules have a chance to slow down. This reduces stress in the glass, so that it becomes more stable and less breakable.
Characteristics of a Genuine Swarovski® Bead.
1. A genuine Swarovski® bead has precise cuts and facets, regardless of size of the design.
2. The colour is consistent for all designs, shape and sizes. Its effects are consistent and could be distinguished from just a naked eye inspection.
3. The crystal contains 32% lead therefore has higher light refraction, that is to say, it has more luster and sparkle than normal glass.
4. It has high degree of clarity when viewed under a magnifying glass, similar to high grade cubic zirconias.
5. It's weight is higher than normal glass or other brands of lead crystal, due to the high lead content.
Goldstone is a type of glittering glass made in the presence of a reducing flame. The finished product can take a smooth polish and be carved into beads, figurines, or other artifacts suitable for semiprecious stone, and in fact goldstone is often mistaken or misrepresented as a natural material.
The most common form of goldstone appears to be reddish-brown, due to the presence of tiny crystals of metallic copper. When the reduced goldstone melt cools, the copper remains in atomic isolation and precipitates into small crystalline clusters which reflect light through the surrounding transparent or translucent glass, rendering the final product effectively opaque.
The manufacturing process for goldstone was discovered in seventeenth-century Venice by the Miotti family, which was granted an exclusive license by the Doge. Persistent folklore attributes the discovery and secret of goldstone to an unnamed Italian monastic order, giving rise to the alternate names "monk's gold" or "monkstone".
Hematite (iron oxide) (hardness 6.5)
Hematite is the mineral form or iron oxide and is not magnetic.
Hematine is an artificial form of hematite. Hematine is magnetic. Although it is claimed by many that it is made from ground hematite or iron oxide mixed with a resin, analysis has proven it to be an entirely artificial compound, a barium-strontium ferrite.
Howlite (hydrated calcium borosilicate) (hardness 3.5)
Howlite is a soft, light mineral with a chalky white colour, commonly with black or brown veins. It is very porous and may be dyed to imitate other minerals, especially Turqoise.
Imperial Topaz (aluminum flourohydroxysilicate) (hardness 8)
Topaz occurs naturally in a range of colours. White/clear (without colour), pink, blue and golden brown. Since pink and blue stones are very rare, almost all gems on the market today are heat treated colourless Topaz. Precious Topaz is the golden brown variety, but the most prized one is Imperial Topaz, the golden brown variety with pink over tones.
Imperial topaz has a rich, golden orange/red, somewhat reddish hue, or pink overtone. Natural pink imperial topaz has been found in Pakistan and Russia. When imperial topaz was first found in Russia, only the czar and his family had ownership rights. The majority of the world's supply of natural non-pink imperial topaz comes from Minas Gerais, Brazil.
Iolite (magnesium aluminum silicate) (hardness 7)
Violet-blue Iolite (also kown as cordierite) has been called water Sapphire because of its similarity to blue sapphire when cut.
For centuries, Jade was thought to be a single gemstone, but in 1863, two types were recognised: Jadeite and Nephrite. Both are tough, fine-grained rocks. Jadeite occurs in a wide range of colours, including green, lilac, white, pink, brown, red, blue, black orange and yellow. The most prized variety is Imperial Jade, a rich emerald green.
Jasper, Chalcedony (hardness 7)
Jasper is a massive, fine-grained, opaque variety of Chalcedony. It occurs in several brown, green and reddish varieties.
Jet (variety of lignite) (hardness 2.5)
Jet is an organic gemstone. Like coal, it was formed from the remains of wood immersed in stagnant water millions of years ago, then compacted and fossilized y the pressures of burial. Jet is black or dark brown but may contain pyrite inclusions.
Kunzite (lithium aluminum silicate) (hardness 7)
Pale pink Kunzite was discovered in 1902 in the Pala District of San Diego County in California. Today, the prism-shaped crystals with their typical vertical striations are mainly found in Afghanistan, Madagascar, Brazil and the USA.
As a variety of spodumen, Kunzite belongs to the class of the chain silicates. It has minute traces of manganese to thank for its fine lilac colour.
Kunzite is the youngest member of the spodumen family, to which the green or yellowish-green Hiddenite, discovered about a quarter of a century earlier, also belongs. These two, together with diopside, jadeite and three other kinds of mineral, the spodumens make up the pyroxene group.
Kyanite (aluminum silicate) (hardness 5 or 7)
Kyanite has two hardnesses, they are softer parallel to the natural cleavage (preferred direction of a natural break) but harder perpendicular to it. Kyanite occurs in green and blue with white and silver.
Labradorite (sodium calcium aluminosilicate) (hardness 6)
Labradorite is truly a fascinatingly beautiful mineral. Its a mineral whose charm is not fully noticed and may be overlooked if not viewed from the proper position. Generally a dull, dark looking mineral with no special virtue until the colorful shiller is observed glowing on the surface. Labradorite can produce a colorful play of light across cleavage planes and in sliced sections called labradorescence. The usually intense colors range from the typical blues and violets through greens, yellows and oranges. Some rare specimens display all these colors simultaneously.
The color display is from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a separating and layering of these two phases. The resulting color effect is caused by a ray of light entering a layer and being refracted back and forth by deeper layers. This refracted ray is slowed by the extra travel through the layers and mixes with other rays to produce a light ray coming out that has a different wavelength than when it went in. The wavelength could correspond to the wavelength of a particular color, such as blue. The effect depends on the thickness and orientation of the layers. If the layers are too thick or too thin no color shiller is seen. Also if the viewer does not observe from the precise angle or if light is not supplied from the proper angle then no color shiller is seen. The labradorescence is truly a one of a kind mineralogical experience and must be observed in person in order to truly appreciate its beauty.
It is worth mentioning that currently large quantities of a translucent white Labradorite, originating in India, is widely sold under the misnomer "Rainbow Moonstone", but it is not a Moonstone.
Lapis Lazuli is a blue rock made up of several different minerals, including lazurite, sodalite, hauyne, calcite and pyrite. The composition and colour of Lapis Lazuli varies, but it is the intense dark blue, with minor patches of white calcite and brassy yellow pyrite, that is considered to be the best quality.
Larimar (also lorimar) is a rare blue variety of pectolite found only in the Dominican Republic, in the Caribbean. Its coloration varies from white, light-blue, green-blue to deep blue. The deep blue variant is known as volcanic blue.
Lepidolite is a lilac-gray or rose-colored phyllosilicate mineral of the mica group that is a secondary source of lithium.
Malachite (copper hydroxycarbonate) (hardness 4)
This vivid green gem gets its colour from the copper in its chemical formula, and its lovely swirling and concentric patterns, from the way forms. The basic mode of formation is precipitation from solution, rather than from the crystallization of melted rock, or from the condensation of vapours.
Technically malachite is termed a "secondary" mineral which means that it is created by a chemical reaction between minerals that have already formed, rather than by a simple one-step process. When waters containing carbon dioxide or dissolved carbonate minerals interact with pre-existing copper-containing rocks, or, alternately, when solutions containing dissolved copper minerals interact with carbonate rocks, malachite may form. Most commonly it occurs in "massive" form as a micro-crystalline aggregate, in nondescript lumps, or as crusts on other rocks. The typically banded appearance reflects the waxing and waning of the solutions necessary for formation, and the frequent changes in their chemical content.
The majority of the world's malachite supply comes from The Democratic Republic of Congo (formerly Zaire), Namibia, Russia and the American Southwest.
Due to its softness it is easy to shape and carve, but unlike many soft minerals, it generally takes a good polish. With attributes like this, there is no wonder that it finds so many decorative uses.
The Victorians were great admirers of opaque jewellery stones, and malachite was one of their favourites, which they sometimes chose to set in gold. For the most part today, though, this gemstone is used in small carvings, beads, and cabochon gems usually set in silver. It is particularly popular in both genuine Native American sterling designs and inexpensive imitations of them.
Malachite is rarely enhanced, although lower quality, less compact pieces may be stabilized with plastic resins or given a surface polish with wax. Although synthetic malachite has been manufactured for research purposes, it has not much been found in the gem marketplace to date. There would be little point, as the synthetic material would be far more costly than the natural mineral which is in abundant supply.
Happily, along with malachite in those secondary deposits are other copper containing minerals which sometimes end up combined in the same specimens. Along with malachite's forest green, the addition of blue-green chrysocolla, dark blue azurite, or brick red cuprite can create rocks of surpassing beauty.
[Malachite and friends: with chrysocolla, with azurite, with cuprite]
Marble is a nonfoliated metamorphic rock resulting from the metamorphism of limestone, composed mostly of calcite (a crystalline form of calcium carbonate). It is extensively used for sculpture, as a building material, and in many other applications.
Meerschaum (hydrated magnesium silicate) (hardness 2.5)
Meerschaum is also known as Sepiolite is a very fine-grained, soft, light rock. It may be white or grey with a yellowish or reddish tinge.
Moissanite is a mineral that was first discovered in fragments of the meteorite at Diablo Canyon or Meteor Crater in Arizona. It was named in honor of its discoverer, Nobel Prize winner Dr. Ferdinand Henri Moissan. Synthetic moissanite is also known as silicon carbide after its chemistry and by the trade name, carborundum. In the meteoritic material, moissanite is associated with tiny diamonds. Moissanite is also the trade name being used for new synthetic SiC gemstones.
Moissanite grown in laboratories is now being cut as gemstones and they are used as diamond simulants. Moissanite brings to the jeweler's table a similar index of refraction and better than twice the fire of diamond, but is only slightly less expensive due to the difficulty in growing the crystals. Moissanite is causing quite a stir in the jewelry markets.
As a diamond simulant, artificial moissanite is very hard to differentiate from diamond and can fool many gemologists. It does have many similarities. It is very hard at 9.25 (diamond is 10) and it is highly refractive with an index of refraction of 2.6 - 2.7 (diamond's IR is slightly lower at 2.42). Most important, moissanite and diamond are thermally conductive unlike other diamond simulants and unfortunately it is this property that is primarily used as the test for the authenticity of real diamonds. Differences however are clear and other tests can be used to differentiate the two.
Mookaite is the common, or popular, name for the rock with the geological name Windalia Radiolarite, being a fine grained, silicified and multi-coloured, radiolarian siltstone, found in outcrops, principally on Mooka Station (a sheep farm of around 700,000 acres)on the west side of Kennedy Range in Western Australia. The Kennedy Range itself is located approximately 90 miles east of Carnarvon and 25 miles to the north west of Gascoyne Junction, a small town of around 60 people, and located at the first (heading west from Carnarvon) sealed crossing of the mighty (usually dry) Gascoyne River.
The semi-precious stones are sometimes advertised as "Mookite", "Mookalite" or "Mookarite"
Moonstone (potassium aluminum silicate) (hardness 6)
Moonstone is the opalescent variety of orthoclase, with a blue or white sheen or shiller. This is caused by the reflection of light from the internal structure, made up of alternating layers of albite and orthoclase feldspar. Thin albite layers give an attractive blue, while thicker layers produce a white shiller.
It is worth mentioning that currently large quantities of a translucent white Labradorite, originating in India, is widely sold under the misnomer "Rainbow Moonstone", but it is not a Moonstone.
Morganite (Beryl) (hardness 7.5)
Coloured by manganese impurities, the pink variety of Beryl is called Morganite, after banker and gem enthysiast, J. Pierpoint Morgan.
Obsidian (silicon dioxide) (hardness 5)
Obsidian is a natural glass. It is formend from volcanic lava that cooled too quickly for significant crystallization to occur. It is amorphous with no cleavage. Obsidian is usually black, but other colours do occur. If internal bubbles of crystals are visible, the effect is called a 'snowflake' effect.
Onyx, Chalcedony (silicon dioxide) (hardness 7)
Onyx is a variety of the microcrystalline quartz Chalcedony. Onyx is similar to Agate, but it has straight rather than curved banding. Onyx has been dyed since ancient times and is available for example in bright green.
The common Opal varieties are available in pastel colours of pink, blue or white. They are opaque and mostly mined in Peru.
Opal, precious (hydrated silica gel) (hardness 6)
Opal is a hardened silica gel, usually containing 5-10% water. It is therefore monocrystalline, unlike most other gemstones, and may eventually dry out and crack.
is a man made glass.
Pearl (calcium carbonate conchioline and water ) (hardness 3)
The only gem grown within a living creature, pearls are completely unique.
Throughout history, pearls have been highly prized and sought after, worn by rulers, emperors and royalty. Until the late 19th century, all pearls were truly natural pearls - found by divers opening wild oysters to see what treasure may lie within. Pearls are formed when a substance or irritant makes its way inside the oyster's shell. The oyster responds to the irritant by laying down layer upon layer of nacre on the surface of the irritant. Nacre (Aragonite) is the iridescent substance found within the oyster's own shell - true mother of pearl. The shape and beauty of the resultant pearl is dependent on the thickness and quality of the nacre. Pearl culturing began in Japan in the late 19th century when it was discovered that the oysters could be artificially implanted with a small bead - usually made of clam shell. The oyster responds to the implant by laying nacre upon this bead (or nucleus) over the following years, producing a pearl which will be more or less round in shape.
Today, almost all pearls we see are cultured pearls. Truly natural pearls are only harvested now around the Persian Gulf, and even these are exceptionally rare. Whilst natural pearls may still be found in pearl jewellery, the cost of such pieces is usually prohibitive for all but the wealthiest consumers. Some antique and estate jewellery, particularly if crafted prior to the 20th century, may be set with natural pearls.
Freshwater Pearls
Freshwater pearls are grown in the molluscs that live in the lakes and rivers in China, where the molluscs are implanted with tiny segments of mollusc mantle tissue. Each mollusc will be implanted with dozens of segments at a time, so that at harvest, many pearls can be produced by a single creature.
Freshwater pearls are the most common pearl, with sizes varying from just 2mm or so, through to 14mm or occasionally more. As they are mostly grown on tissue implants, rather than a bead nucleus, freshwater pearls are comprised entirely of nacre - resulting in high levels of lustre, and greater durability. Freshwater pearls can naturally be white, peach, pink, lavender and purple, but are frequently colour treated to produce black and grey pearls.
Up until the early 1990's, freshwater pearls were almost always very small and irregular in shape, and not highly valued. Whilst baroque (free form) and oval shapes are very common, and popular, in freshwater pearls, truly round pearls are now available in all sizes. These more desirable pearls still account for only a small proportion of the total harvest of freshwater pearls, and as such, are considered both rare and valuable.
Chinese pearl farmers are also experimenting with using a bead nucleus within their molluscs to produce pearls of varying shape. So called coin pearls are an example of this - with layer upon layer of lustrous nacre being formed around a disc-shaped implant. Larger sizes of freshwater pearl are also starting to be produced by farmers using a round implant - these pearls can be up to 18mm or so in size, and at this time, are extremely rare.
Akoya Pearls
Akoya pearls were traditionally grown only in Japan, but now are grown also on China's east coast, and on the coastal waters of Vietnam, and even on the east coast of Australia. They are a small, (usually not larger than 8 or 9 mm) and usually very round, pearl, and were the first pearl to be cultured commercially. The famous Mikimoto brand is well known to us all. These pearls are prized because of their highly shiny and reflective surface and are still highly valued and desired.
Tahitian Pearls
These stunning pearls are grown in the equatorial waters of Tahiti and around the Cook Islands, and come in every tone of grey and black. These pearls have the most beautiful overtones - the extra colours that seem to come from within the pearl itself. Pink, purple, green, copper and silver are just some of the overtones seem on Tahitian pearls. Tahitian pearls are grown on a bead implant - made of carved clam shell - and can be up to 18 mm or slightly more in size. Whilst often very round, drop and oval shaped Tahitians are much more common, and beautiful ringed pearls are also highly desirable.
South Sea Pearls
South Sea pearls are the most valuable cultured pearl available. They are grown in the waters off Australia's North West Coast, and along the Southern Coasts of the Indonesian Islands. They are the largest pearl commercially available, with sizes up to 20mm being quite typical. Production times are long, and production techniques difficult, making South Sea pearls the most expensive to produce. Colours of South Sea pearls vary from silvery white, a platinum blue-white, cream, pale gold, and a true rich deep gold.
Fully matched strands of South Sea pearls remain one of nature's true treasures.
Pearl Shapes
Round Pure round pearls are still the rarest shape of pearl, and therefore, the most desirable. Only a very small proportion of all farmed pearls are truly round, and their higher price reflects their rarity.
Semi round Pearls that are very slightly ovoid in shape, but not perfectly round, and not so irregular as to be known as baroque pearls are usually termed semi round. Pearls of this shape usually appear round when worn, and these pearls will still command a high price.
Baroque The term baroque simply means "freeform", and so pearls of this type are usually highly irregular in shape. Well matched strands of baroque pearls will still attract a premium price, although not nearly so high as for round pearls.
Rice, oval Rice or oval pearls are generally smaller in size, and less expensive to purchase. Their symmetrical shape makes them attractive for artisan and hobby jewellers, whilst their more informal appearance makes them a great shape for younger pearl wearers.
Other useful terms:
Keishi - Keishi pearls can be formed by all types of pearl-growing oysters and molluscs. A keishi pearl forms when the host mollusc rejects the implant or nucleus, and expels the irritant from the pearl sac. A pearl then forms outside the pearl sac. This "reject" pearl is usually a very highly lustrous pearl, often displaying orient, and is comprised of 100% nacre. These pearls, whether they are South Sea keishis, Tahitian keishis or Freshwater keishis, are highly sought-after, and, particularly in larger sizes, are very rare.
Bead-nucleated - All seawater pearls, whether they be Akoyas, Tahitians or South Seas, are cultured on a bead nucleus. However, some freshwater pearls have recently been cultured on a bead nucleus, with the result being frequently larger sized pearls, or pearls with a "tail" attached. Pearls with such a tail are also sometimes referred to as flameball , or fireball pearls.
Coin pearls - The name given to freshwater pearls grown on a flat disc-shaped nucleus. Occasionally, special shapes of implant are used, to produce rectangular, square or even petal or star shaped pearls!
Mabe - Mabe pearls are hemispherical pearls, cut from the inside of an oyster's shell, then filled and backed to produce a beautiful, lustrous, domed pearl. These pearls are cultured by implanting a hemispherical bead against the oyster's shell, around which the nacre is deposited.
Peridot (magnesium iron silicate) (hardness 6.5)
Gem-quality specimens of the mineral Olivine are called Peridot. The olive- or bottle green colour of Peridot is due to the presence of iron.
Pietersite, Blue Pietersite is sometimes called "Hawk's Eye" or "Eagle's Eye", was discovered by Sid Pieters in 1962 while he was prospecting some farm land in Namibia, Africa. After his discovery, he registered the find in the mineral records of Britain. Currently there are only two known sources of Pietersite; China and Africa. These two forms of Pietersite, are similar, but still somewhat different from each other. The China Pietersite exhibits slightly different color variations from Mr. Pieters' original mineral, but both are beautiful and are now universally recognized as Pietersite.
While Pietersite has the lovely chatoyancy of tiger eye, it is not found in continuously structured bands or fibers, more in swirls, swathes and fibrous (sometimes linear) segments. Thus the structure of the fibrous streaks in Pietersite may appear rather chaotic, and can flow or exist in many directions side-by-side like bold paint strokes.
Prasiolite, Green Amethyst (hardness 7)
Prasiolite, green-quartz or vermarine is a green form of quartz. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, but it is seen in Lower Silesia in Poland. The gem has a refractive index of 1.54-1.553. [1] It is usually produced artificially by heat-treating amethyst.
The terms green amethyst and greened amethyst are considered misnomers by gemologists.
Prehnite (calcium aluminum hydroxysilicate) (hardness 6)
Often an oily green, Prehnite may also range from pale yellowish to brown. Some pale yellowish brown Prehnite is fibrous enough to be cut as a cabochon and may show the cat's eye effect.
Pyrite (iron sulfide) (hardness 6)
With its brassy yellow colour, Pyrite is often mistaken for gold, hence the other name, fool's gold. Pyrite is fairly brittle so requires some care when handling.
These 'stones' usually have rather fancy names. Strawberry Quartz, Pineapple Quartz, Emerald Quartz, Coffee Quartz and so on. One thing they all have in common: they are synthetic.
These are man-made stones, using natural stone material and colour.
Rhodochrosite (manganese carbonate) (hardness 4)
Rhodochrosite derives its beautiful pink colour from manganese. Gem-quality material shows almost no white or black banding, but even stones with banding are quite attractive and valuable. Main deposits are in Argentina and Peru.
Rhodonite (manganese silicate) (hardness 6)
Rhodonite has a distinct pink colour, although material with black veins is a bit more popular. Transparent crystals are rare and fragile.
Rock Quartz Crystal (silicon dioxide) (hardness 7)
Colourless and transparent, Quartz is one of the most common minerals of the Earth's crust. As always, beautiful specimen - internally flawless and beautifully cut and polished - will command superiour prices (top row of stones).
Rose Quartz (silicon dioxide) (hardness 7)
Small amounts of Titanium colour this Quartz variety a beautiful soft rose. Superior material is mined in Madagascar. Transparent stones are very rare.
Rubellite (complex borosilicate) (hardness 7.5)
Rubellite is a member of the Tourmaline family and consist of the pink or red varieties.
Ruby (aluminum oxide) (hardness 9)
Ruby is the name given to red, gem-quality corundum.
Rutilated Quartz (silicon dioxide) (hardness 6)
Rutilated Quartz derives its name from the tiny, needle-like strands of a material called 'rutile' that becomes embedded in the Quartz crystal, forming fascinating multiple inclusions.
'Rutile' is a crystalized mineral that is composed of titanium dioxide which crystallized in the tetragonal crystal system, usually forming into a prismatic or twinned configuration.
Sapphire (aluminum oxide) (hardness 9)
All gem-quality corundum that is not red is called sapphire. Most valuable is the orange-pink variety, called Padparadscha Sapphire (right photo).
Serpentine (magnesium hydroxysilicate) (hardness 5)
The name Serpentine refers to a group of predominantly green minerals that occur in masses of tiny intergrown crystals.
Shell (calcium carbonate) (hardness 2.5)
Shells come in a variety of sizes, shapes and colours. Conch shells with pink and white layers can be carved into attractive cameos.
Smokey, smoky Quartz (silicon dioxide) (hardness 7)
Smokey Quartz is the name for the brown variety of Quartz. Also available are Beer Quartz, Whiskey Quartz and Olive Quartz. These are natural Quartz varieties with slightly different shades of brown/green Quartz.
Spectrolite (sodium calcium aluminosilicate) (hardness 6)
This brilliantly iridescent material is regarded as the world's most beautiful form of labradorite (a variety of plagioclase feldspar). Specifically, "spectrolite" is a trade name for high-grade labradorite found only in Finland. While standard labradorite has a light green-gray base and moderate play of color (called labradorescence or schiller), spectrolite has a dark or black base and reflects an entire spectrum of colors. Blue is spectrolite's most common play of color, followed by a range of yellows: lime-yellow to gold to bright canary yellow. Orange and green also can be seen and, more rarely, red, magenta and purple. Composed of calcium sodium aluminum silicate, spectrolite is a versatile gemstone.
Its brilliant pastels and deep gold colors make it perfect for spring and summer wardrobes. Every movement creates a shifting pattern of surface colors. Spectrolite is heat sensitive, prone to splitting and has medium hardness; it is therefore relatively fragile and must be worn and cleaned with care. Ultrasonic or steam cleaning is too risky, and beads to be used in bracelets should be worn carefully and infrequently. The best uses for this stone are earrings, brooches and pendants, which are worry free.
Spectrolite was discovered by accident in 1940 during World War II, as stone was being quarried along Finland's eastern border to create tank obstacles. This makes it a more recent discovery than the well-known labradorite from Canada and Madagascar. Countries are allowed to name their own gemstones, and so Finland was faced with an opportunity. Professor Aarne Laitakari, then director of the Geological Survey of Finland, selected the name "spectrolite." This choice reportedly stemmed from the stone's wide spectrum of colors. It's also said that each color symbolizes a trait of Finland: blue represents the thousands of lakes; green suggests the forested wilderness; and yellow, red and orange reflect the glow of fall foliage. Spectrolite is now Finland's national stone. Metaphysical properties associated with spectrolite include providing clarity to the inner self, enhancing patience, dispelling negativity, improving cooperation and giving perseverance and strength. It is also purported to help treat eye and brain disorders, and to help regulate metabolism and the digestive process.
Sodalite (sodium aluminum silicate) (hardness 5.5)
Sodalite is found in all shades of blue and is a major constituent of the rock Lapis Lazuli. Sodalite very rarely contains Pyrite inclusions.
Spinel (magnesium aluminum oxide) (hardness 8)
Spinel occurs in a wide range of colours, with red being the most popular (coloured by chromium and iron).
Sugilite (also known as luvulite) is a relatively rare pink to purple cyclosilicate mineral. Sugilite can range from a dark blackish purple, to some shades of pink. It does not form well shaped crystals but is mostly found in massive (irregularly shaped mass with no apparent crystal habit) shapes.
Usually found in Iwagi Island, Shikoku, Japan as well as Mont Saint-Hilaire, Quebec, Canada and South Africa.
Commonly known as "Purple Turquoise" even though the two stones are not related (When gemstone seller name a stone after another stone it is mostly done to increase the price).
Named after Ken-ichi Sugi, a Japanese Geologist in 1944, Sugilite has become a fairly popular stone.
Sunstone, Oligoclase (sodium calcium aluminosilicate) (hardness 6)
This gemstone variety of feldspar has minute platelike inclusions of iron oxide (hematite or goethite) oriented parallel to one another throughout. The reflections from these inclusions give the mineral (usually the plagioclase feldspars albite, oligoclase, or labradorite, but sometimes the alkali feldspar orthoclase) a spangled appearance and often a reddish glow.
Highest quality material is mined in Oregon, USA.
Tanzanite (calcium aluminum hydroxysilicate) (hardness 6.5)
Tanzanite is an extraordinary gemstone. It occurs in only one place worldwide. Its blue, surrounded by a fine hint of purple, is a wonderful colour.On its discovery in 1967, it was enthusiastically celebrated by the specialists as the 'gemstone of the 20th century'. They held their breath in excitement as they caught sight of the first deep-blue crystals which had been found in the Merelani Hills near Arusha in the north of Tanzania. Millions of years ago, metamorphic schists, gneisses and quartzites formed impressive, flat-topped inselbergs on a vast plain in the shadow of Kilimanjaro. The precious crystals grew in deposits on the inside of these unusual elevations. For a long, long time they were hidden from the eye of Man, until one day some passing Masai shepherds noticed some sparkling crystals lying in the sun and took them along with them.
In Merelani today, the search is carried on for the coveted crystals in several, smallish mines, in some cases using modern methods. As a rule, only small grains are found, but now and again the mineworkers succeed in fetching out a larger crystal.
Tiger Iron is almost exclusively valued as a decorative gemstone. Its rich and striking beauty is created by three gemstones that nature has combined to create tiger iron. Tiger's eye, hematite and jasper exist in layers to form this composite gemstone.
Ironstone (Fe) is plentiful and accessible. Jasper exists in a variety of colors. It is made up of mineral oxides that create bands and patterns of color. Tiger's Eye is natural asbestos. During volcanic events, the fibrous asbestos is replaced by iron-bearing quartz called limonite. This is what creates the dazzling golden luminous eye of the tiger that provides such elegant beauty in tiger eye gemstone. The glamour of tiger iron gemstone is created by what is known as chatoyancy. This is a French word meaning "cat's eye". It is an optical reflectance that gives a sense of depth, shape and shine between the fibrous layers of crystal.
In order for chatoyancy to occur in a gemstone, it must be cut in cabochon style. This requires the stone be cut so the fibrous crystal layers are parallel to the base of the polished gemstone.
Topaz (aluminum fluorohydroxysilicate) (hardness 8)
Most blue and pink varieties are derived from colourless Topaz that has been heat treated. Only precious Topaz (golden brown), colourless Topaz and Imperial Topaz (orange pink) are available in their natural colour.
Tourmaline (complex borosilicate) (hardness 7.5)
Tourmaline is available in a vast range of colours, even combining two colours in one stone (pink and green) which is calles 'Watermelon Tourmaline'. The brown green stones to the right in the photo are called 'Petro Tourmaline'.
Tsavorite (calcium aluminum silicate) (hardness 7)
Tsavorite is the name for the transparent green grossular Garnet variety.
Turquoise (hydrated copper aluminum phosphate) (hardness 6)
Turquoise is one of the first gemstones to be mined. Turquoise is opaque to semitranslucent, light and very fragile. Some material is very porous, leading to fading and cracking so it may be impregnated with wax or resin. Most Turquoise these days is stabilized to prevent the popular light blue colour turn gree over years.
Unakite (calcium aluminum iron hydroxysilicate) (hardness 6.5)
Unakite is a rock containing mainly Epidote, a yellow, green mineral. Unakite shows lovely pink veins and patterns apart from the green Epidote.
Vesuvianite, Idocrase (calcium aluminum silicate) (hardness 6.5)
Vesuvianite was first discovered on the Italian volcano Vesuvius. Colours are red, yellow, green, brown or purple.
This is real natural volcano lava rock.
Zircon (zirconium silicate) (hardness 7.5)
Zircon is a natural stone with a hardness of 7.5 (between Quartz and Topaz). It is most famous for its colourless stones, which have been used to resemble diamonds, but also occurs in yellow, orange, blue, red, brown and green varieties.
Zoisite (calcium aluminum hydroxysilicate) (hardness 6.5)
This is a massive green variety of the mineral Zoisite which contains rubies.
