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Agate

The name agate is derived from the river Achates in Sicily.

Agate is the name given to a wide selection of varieties of chalcedony, a form of quartz, which is cryptocrystalline. Microscopically small crystals of quartz are embedded in opal, which is hydrated quartz. The proportion of quartz to opal varies, and this variation is reflected in differing densities, refractive indexes and other properties. The quartz crystals are in a fibrous form, sometimes running approximately parallel to each other, sometimes entwined.

The names for chalcedony and agate are somewhat interchangeable, although the term agate is usually used to describe the banded varieties of chalcedony. Many agates are naturally coloured, others are stained for decorative effect.

Agate can be many different colours, and because it’s banding is so variable, different types of it have been given many different descriptive names. It is often used to make quite large decorative items. Some names include moss agate and picture agate. Many types of organic material have been fossilised by agate, where the organic material has been replaced slowly over a long period of time, so that the original structure of the original item is retained. Fossilised or petrified wood is an attractive form of agate.

Deposits can be found in South America and were once found in Germany but mines have been exhausted.

Amethyst

Amethyst is the clear purple, mauve or violet form of the mineral quartz. As such it is related to citrine which is the yellow form of quartz, and also to rock crystal which is the colourless variety.

It is possible for some specimens of quartz to be different colours in different areas. Amethyst and citrine are varieties of quartz which can both occur in the same stone.

As with other gemstones, the "best" colour can vary according to personal preference, and the quality of amethysts can vary considerably. The most important attribute should be an attractive colour. The rich deep violet colour is generally the favourite and most expensive, but a stone of medium colour intensity, with plenty of sparkle, can also be very attractive.

Amethyst gets its name from a Greek word amethustos meaning "not drunken", as it was believed to protect against intoxication by alcohol.

The most important deposits of amethysts are in Brazil, Madagascar, Zambia, Uruguay as well as Burma, India, Canada, Mexico, Namibia, Russia, Sri Lanka and the U.S.

Amazonite

Amazonite (derived from the Amazon is an opaque sodium feldspar. Colour distribution is irregular; lustre is vitreous; it is sensitive to pressure. The colour is green to blue-green.

Deposits are found in Colorado (United States), Brazil, India, Kenya, Madagascar, Namibia, and Russia.

Andalucite

Andalucite is named after Andalucia in Spain. The colours range from yello-green, green to brownish-red.

Deposits are found in Australia, Brazil, Canada, Russia, Spain |(Andalucia), Sri Lanka, and the United States.

Apatite

The name of apatite (Greek – cheat) because it can be easily confused. It has a vitreous lustre, sensitive to acids. It can be easily confused with andalusite, brazilianite, precious beryl, topaz and tourmaline.

The colour ranges from colourless, pink, yellow, green, blue and violet.

Deposits can be found in Burma, Brazil, India, Kenya, Madagascar, Mexico, Norway, Sri Lanka, South Africa, and the U.S.

Aquamarine

Aquamarine (Latin – water of the sea) is so named because of its seawater colour. Aquamarine is the sky blue or sea blue variety of beryl; sometimes it is sea green, and less desirable.

Aquamarine jewellery can be carefully cleaned using warm soapy water, or detergent, rinse thoroughly afterwards as detergents can cause dermatitis and allergic reactions. Enzyme cleaners should be avoided for the same reasons. Brushing with an old tooth brush to remove dirt and grease will also help. Cleaning agents containing chlorine may have a detrimental effect on low carat gold alloys, so are best avoided.

The most important deposits are found in Brazil. The well known deposits in Russia and the Urals seem to be worked out. Other deposits of local importance are in Australia, Burma, China, India, Kenya Madagascar, Mozambique, Namibia, Nigeria, Zambia, Zimbabwe, Sri Lanka, Tanzania, and the U.S.

Beryl

Beryl exists in a number of different varieties, some being better known by their own name, for example, emerald is the grass green variety and aquamarine is the sky blue variety.

Pure beryl is colourless, often called white, and although quite rare, tends not to be valuable because it does not have much brilliance. Colours, as in many gemstones, are caused by small amounts of impurity, usually metallic oxides. This is another case where impurity is desirable.

The name beryl comes from India and has always been associated with the gemstone.

Deposits are found in Brazil, Austraila (Queensland), Burma (Myanmar), China, India, Kenya Madascar, Mozambique, Namibia, Nigeria, Zambia, Zimbabwe, Sri Lanka Tanzania and the United States.

Yellow Diamonds

Some people believe that yellow means poor quality as far as diamonds are concerned, and that the best diamonds are completely colourless. The view demonstrates that a little learning is dangerous. What matters more is personal preference not received dogma. All colours have different psychological effects. Yellow is a high attention colour, and can be perceived more quickly than other colours, for this reason it is often used for safety clothing. Yellow is not, for most people, a high preference colour, so it is not as popular as other colours for gemstones. Strangely, if you asked most people for a list of their favourite colours, they would list blue, red, green, pink, amongst their favourites. Hardly anybody would list white, yet so many people insist that they only wear diamonds, and don't wear coloured stones.

Black and White Diamonds

Black and white diamond jewellery became fashionable in the late 1990's in stone sizes of a few points to several carats. Demand for natural black diamonds soon exceed supply. As black boart is also difficult to polish, the demand for black diamonds has been met by the supply of treated black diamonds.

Colour in natural black diamonds can be the result of polycrystaline structure, the presence of (possibly sulphide) inclusions, and extensive cracking.

Black diamonds have been around for a long time, and in the last few years have started to be marketed and promoted, making them start to be fashionable.

Blue Diamonds

The blue diamond is a beautiful bright stone. Natural fancy blue diamonds are extremely rare and expensive. Some people might think that if they wanted a blue stone they could buy a sapphire, and they would be quite right, although this is a very unimaginative way of thinking. It would be very difficult to find a sapphire as bright and attractive as a diamond, and even if it were possible to find a sapphire as intense and as sparkly, it would be very expensive. Also, although sapphires are very hard, they are nowhere near as hard as diamonds.

Carnelian

Carnelian is a red variety of chalcedony which is cryptocrystalline quartz. Its red colour is due to the presence of iron impurities in the form of iron oxide or hematite. It can vary from a flesh red to a clear red. It is usually cut en cabochon, or into beads, and is also used for intaglios and cameos. Imitations of carnelian are made by the staining of agate.

Originally found in the deserts of Arabia and Egypt, it has also been found in the Rio Grande area, India, China, Colombia, Saxony, Scotland, West Germany and USA.

Chalcedony

Chalcedony is a form of quartz which is cryptocrystalline. It is name after an ancient town at the Bosporus and consists of microscopic fibers, which are paraleel to each other. It is porous and therefore be dyed. The trade also offers paraleel layered, artificial blue-coloured agate as chalcedony. In ancient times it was used for cameos; today it is used for rings and necklaces.

The colour range is bluish, white or gray.

Deposits are found in Brazil, India, Madagascar, Namibia, Zimbabwe Sri Lanka, Urugay and the United States (California).

Chrysoprase

Chrysoprase is a green variety of chalcedony which is cryptocrystalline quartz. Its green colour is due to the presence of nickel impurities in the form of oxides or silicates of nickel. It can vary from a greenish yellow to a clear apple green.

Chrysoprase was known from ancient Greek and Roman times, although its ancient source is not known. It has been found at Zabkowice in Silesia, the Urals, California, and other parts of the USA.

Citrine

Citrine is the clear yellow or golden form of the mineral quartz. As such it is related to amethyst which is the purple form of quartz, and also to rock crystal which is the colourless variety.

It is possible for some specimens of quartz to be different colours in different areas. Amethyst and citrine are varieties of quartz which can both occur in the same stone. As our photograph clearly shows, the difference in colour at the two ends create a striking contrast. Such stones are sometimes called ametrines.

CZ or Cubic Zirconia

Cubic zirconia, often abbreviated to CZ, is a synthetic stone used as a diamond simulant.

It is the oxide of the metallic element zirconium. Zirconium dioxide, known as baddeleyite, is found as a naturally occurring mineral, but with a different, monoclinic, crystalline structure. Cubic zirconia should not be confused with zircon, which is a rare naturally occurring gemstone.

It was first produced in 1977, and was originally marketed under the trade name of "Djevalite".

CZ is quite hard, and retains its sparkle and polish well. It should not be allowed to rub against other gemstones, particularly diamonds, because this will cause wear and scratching. This should be common sense, and applies equally to all other gemstones.

Druzy

The term "Druzy" refers to the small crystals that are usually formed on the inside of geodes. When water carrying dissolved silica is forced into a cavity in a rock and rapid cooling occurs, these tiny crystals are formed on the surfaces of the rock cavity and form druzy. The surface looks a lot like a large collection of crystals of colored sugar. They glisten and shine when the stone is moved or when the light source moves.

Emerald

The name emerald derives from Greek smaragdos. It means “green stone” and, in ancient times, referred not only to emeralds, but also probably to most green stones.

Emerald is the most previous stone in the beryl group. Its green is incomparable and is therefore called “emerald green”. The colour distribution is often irregular; a dark green is most desired, but quite a few bluer emeralds are marketed today.

Only the finest specimens are transparent. Often the emerald is clouded by inclusions. These are not classified as faults, but are evidence as to the genuineness of the stone as compared with synthetic and other imitations. The expert refers to these inclusions as jardin (French – garden).

All emeralds are brittle and combined with internal stress sensitive to pressure; care must be taken in heating them. They are resistant to all chemicals which are normally used in the household.

Emeralds are formed by rising magma and metamorphism. Deposits are therefore found in or near pegmatite veins.

Significant deposits are in Colombia, especially the Muzo mine northwest of Bogota. Mined by the Incas, the Muzo deposit was abandoned and rediscovered in the 17th century.

Another important Colombian deposit, the Chivor Mine, is northeast of Bogota. It was also mined by the Incas.

During recent decades further emerald deposits have been found in Colombia.

Further emerald deposits are in Afghanistan, Australia (New South Wales, Western Australia), Ghana, India, Madagascar, Malawi, Mozambique, Namibia, Nigeria, Pakistan, Zambia, Tanzania, and the United States (North Carolina).

Garnet

This is a group of differently coloured minerals with similar crystal structure and related chemical composition. The name derives from the Latin for grain because of the rounded crystals and similarity to the red blossoms of the pomegranate tree.

Garnet, in the popular sense, is usually understood as the red “carbuncle stones” pyrope and almandine.

Although popularly known as a red stone, the garnet has a range of colours – green, yellow, brown and red.

Deposits are found in Burma, china Madagascar, Sri Lanka, South Africa, Tanzania, and the U.S.

Golden Beryl

Golden beryl is of the precious beryl group of gemstones which refers to all colour varieties that are not green (as in an emerald) or aquamarine blue (as in an aquamarine).

The colour varies between lemon-yellow and golden-yellow. Inclusions are rare.

Deposits can be found in Madagascar, Nambia, Nigeria, Zimbabwe, and Sri Lanka.

Iolite

Gem quality iolite approaches the blue colour of sapphire, and used to be inaccurately called water sapphire. It is a complex magnesium aluminium silicate, with the magnesium partially replaced by ferrous iron and manganese, and the aluminium replaced partially by ferric iron. This makes constants for iolite quite variable.

Iolite is also known as dichroite and cordierite.

The colour normally associated with iolite is blue, and its name comes from the Greek word meaning violet. Iolite also has other colours, which we will explain under the next section pleochroism.

Deposits can be found in Ceylon, Burma, Madagascar, India, Canada and California.

Kyanite

Name (Greek – blue) because of its colour. It has a vitreous luster, often with irregular streaks.

Deposits can be found in Burma, Myanmar, Brazil, Kenya, Austria, Switzerland, Zimbabwe, and the United States.

Labradorite

Labradorite is a gem variety of plagioclase feldspar. It is usually polished as a cabochon. Its beauty as a gemstone is mainly because of its iridescence which is caused by interference effects of light due to fine lamellae (layers or plates) formed by repeated twinning of its crystals, and also by the inclusion of tiny platelets of impurities such as magnetite, an iron oxide.

The body colour of labradorite is grey, and the iridescent lustre is usually blue and green, but yellow, gold, red and purple are among the other irridescent colours displayed. The flashes of colour in labradorite have been compared to the wings of tropical butterflies.

Moonstone

A potassium feldspar gemstone with white shimmer, similar to moonshine (therefore the name).

It has a vitreous lustre and is sensitive to pressure.

Deposits can be found in Sri Lanka, also Burma, Brazil, India, Madagascar and the U.S.

Opal

Opal is a paradoxical gemstone, and one of the most fascinating. It is a form of quartz, but is not a form of quartz. Quartz is very common, yet has many rare and precious gem varieties. Opal itself has numerous varieties. It is the most colourful gemstone, but some forms are colourless. It can be very bright and beautiful, and it can be dull and dead. It is best known for its flashes of colour, but some varieties have no flashes of colour, and are still opals. It can be black, and it can be white. Its best known attribute, the brilliant flashes of many colours, are not called opalescence, but irridescence. Some people think opal is unlucky, but it is one of the most valuable and desirable of gems.

Opals were known and mined in Roman times. The Roman mines were in and around Cervenica, previously in Czechoslovakia, although we have now lost track of all the recent changes in Balkan geography.

Peridot

The name derives from Greek, but the meaning is uncertain. Perhaps it refers to the numerous crystal planes of the crystal. The name chrysolite (Greek – gold stone) was formerly applied not only to peridot but also to many similarly coloured stones. The name commonly used in mineralogy is olivine (because of its olive-green colour). Bright golden green, it can vary to darker green or greenish yellow.

It was originally found on Egypt's St. John's Island once known as Topazios, in the Red Sea, which is now known as Zeberget. It is also found in Burma, Sri Lanka, USA and Norway.

It has been mined for over 3500 years but forgotten for many centuries, and rediscovered only around 1900. Beautiful material is also found in the serpentine quarries in upper Burma. Other deposits have been found in Australia, Brazil, china, Kenya, Mexico, Pakistan, Sri Lanka, South Africa, Tanzania and the U.S. In Europe, the most important deposits are in Norway, north of Bergen.

Peridot was brought to Central Europe by the crusaders in the Middle Ages, and was often used for ecclesiastical purposes. It was the most popular stone during the baroque period.

Pyrite

Pyrite (Greek – fire, as it produces sparks when knocked) is wrongly called marcasite in the trade. True marcasite is a mineral, in many ways similar to pyrite, but unsuitable for jewellery, as it sometimes powers in air. Because of its similarity to gold, pyrite is often called fool’s gold. It is metallic and shiny.

Deposits can be found in Peru, also in Bolivia, Mexico, Romania, Sweden, and the United States (Colorado).

Ruby

Ruby is thus named because of its red colour (Latin – rubeus). It was not until about 1800 that ruby as well as sapphire, was recognised as belonging to the corundum group of gemstones. Before that date, red spinel and the red garnet were also designated as ruby.

The red colour varies within each individual deposit, so it is not possible to determine the source area from the colour. The designations “Burma ruby” or “Siam ruby” are therefore strictly erroneous, and refer more to quality than origin. The most desirable colour is the so-called “pigeon’s blood”, pure red with a hint of blue. The distribution of colour is often uneven, in stripes or spots. As a rough stone, ruby appears dull and greasy, but when cut, the lustre can approach that of a diamond.

Inclusions are common. They are not indicative of lower quality, but show the difference between a natural and a synthetic stone.

The most important deposits are in Burma (Myanmar), Thailand, Sri Lanka, and Tanzania. For centuries, the most important have been in Upper Burma near Mogok.

There are some unimportant deposits in Afghanistan, Australia (Queensland, New South Wales), Brazil, India, Cambodia, Kenya, Madagascar, Malawi, Nepal, Pakistan, Zimbabwe, the United States (Montana, North Carolina), and Vietnam. There are small ruby deposits in Switzerland (Tessin), in Norway, and along the southwest coast of Greenland.

Sapphire

The name sapphire (Greek – blue) used to be applied to various stones. In antiquity and as late as the Middle Ages, the name sapphire was understood to mean what is today described as lapis lazuli. Around 1800 it was recognised that sapphire and ruby are gen varieties of the corundum group. At first only the blue variety was called sapphire, and corundums of other colours (with the exception of red) were given special, misleading names, such as “Oriental peridot the green variety or “Oriental topaz” for the yellow type.

Sapphires are usually light blue, with a tinge of violet. Today corundums of gemstone quality of all colours except red are called sapphire. Red varieties are called rubies. The various colours of sapphire are qualified by description, e.g., green sapphire or yellow sapphire. Colourless sapphire is called leuko-sapphire (Greek – white), reddish to orange-yellow sapphire Padaradschah (Sinhalese for “Lotus Flower”).

There is no definite demarcation between ruby and sapphire. Light red, pink, or violet corundums are usually called sapphires, as in this way they have individual values in comparison with other colours. The colouring agents in blue sapphire are iron and titanium; and in violet stones, vanadium. A small iron content results in yellow and green tones; chrome produces pink, iron and vanadium orange tones. The most desired colour is a pure cornflower-blue. In artificial light, some sapphires can appear to be ink-coloured or black-blue.

Inclusions of rutile needles result in a silky shine; oriented, i.e., aligned, needles (sometimes also very fine fissures) cause cat’s eyes or a six rayed star – a star sapphire.

Today the economically important sapphire deposits are in Australia, Burma (Myanmar), Sri Lanka and Thailand. The most desired sapphires used to come from Kashmir where the deposits were situated at a height of 16,500 ft (5000 m) in the Zaskar region. Production varied since 1880, and the deposits have apparently been worked out. Most stones sold today as Kashmir sapphire come from Burma. In 1984 sapphire deposits were discovered in Montana (United States). There are also deposits in Brazil, china, Cambodia, Malawi, Nigeria, Zimbabwe, and Tanzania. Isolated star sapphires have been found in Finland (Lapland).

Smoky Quartz

Named after its smoky colour. Very dark stones are called “morion” and “caimgorm”. Smoky yellow quartz also occurs. The color of smoky quartz is variable from brown to black and sometimes smoky gray colored specimens are included as smoky quartz. The cause of the color of smoky quartz is in question but it is almost certainly related to the amount of exposure to radiation that the stone has undergone. Natural smoky quartz often occurs in granitic rocks which have a small but persistent amount of radioactivity. Most smoky quartz that makes its way to rock shops and to some gem cutters has been artificially irradiated to produce a dark black color.

The name smoky topaz is improper and no longer acceptable in the trade.

Deposits can be found in Brazil, Madagascar, Russia, Scotland, Switzerland, and Ukraine.

Specitite

Specitite is a mineral that is said to be as rare as Tanzanite and is used in making expensive ornaments, bracelets, rings and other products. They are garnets that are orangey or deep red in colour.

Deposits are found in the remote parts of the Ngorongoro district of Tanzania.

Tanzanite

The name tanzanite (after the East African state of Tanzania) was introduced the New York jewellers, Tiffany & Co.

In good quality the colour is ultramarine to sapphire blue; in artificial light, it appears more amethyst violet.

The only deposit in Tanzania is near Arusha.

Topaz

Formerly, the name topaz was not applied consistently or specifically; one called all yellow and golden-brown, and sometimes also green gemstones topaz. The name topaz is most probably derived from a place of discovery on an island in the Red Sea, now Zebirget but formerly Topazos.

Topaz is well known to be yellow, and in ancient times all yellow stones were called topaz. Nowadays we know better. Topaz can also be colourless, blue, green, pink, orange or brown.

The classical precious topaz is yellow or yellow to orange-brown in colour.

Deposits can be found in Brazil – the most important supplier. Other deposits are in Afghanistan, Australia, Burma, China, Japan, Madagascar, Mexico, Namibia, Nigeria, Pakistan, Russia, Zimbabwe, Sri Lanka and the U.S. Light blue topazes are found also in Northern Ireland, Scotland, and Cornwall.

Tourmaline

Even though tourmaline has been known since antiquity in Mediterranean region, the Dutch imported it only in 1703 from Sri Lanka to Western and Central Europe They gave the new gemstones a Sinhalese name, Turamali, which is thought to mean “stone with mixed colours”.

Tourmaline exists in more colours than any other gemstone. The most desirable colours are pink, intensive pink and green.

Because of the naturally occurring shape, tourmalines are often cut as long baguettes, emerald cuts, or ovals. Large size tourmalines are more relatively common compared with other gemstones, so they are ideal for large jewellery pieces. As with all gemstones, the most attractive colours and qualities are more expensive than lower qualities, and large desirable pieces are not cheap.

The most important supplier is Brazil. Other deposits are in Afghanistan, Australia, Burma, India, Madagascar, Malawi, Mozambique, Namibia, Nepal. Nigeria, Pakistan, Russia, Zambia, Zimbabwe, Sri Lanka, Tanzania, the U.S. and Zaire. In Europe there are tourmaline deposits on Elba and in Switzerland.

Turquoise

The name turquoise means “Turkish stone” because the trade route that brought it to Europe used to come via Turkey.

Pure blue colour is rare; mostly turquoise is interspersed with brown, dark gray or black veins of other minerals or the host rock. Such stones are called turquoise matrix.

A negative change in colour can be brought about by the influence of light, perspiration, oils, cosmetics and household detergents. Turquoise rings should be removed before hands are washed.

The best qualities are found in deposits in northeast Iran near Nisapur. Further deposits are found in Afghanistan, Argentina, Australia, Brazil, China, Israel, Mexico, Tanzania, and the U.S.

Zircon

Zircon hs been known since antiquity, albeit under various names. Today’s name is most likely derived from the Persian language (“golden coloured”). Because of its high refractive index and strong dispersion it has great brilliance and intensive fire. It is britlle and therefore sensitive to knocks and pressure. The lustre is vitreous to a brilliant sheen.

Zircons range in colour from colourless, yellow, brown, orange, red, violet, blue and green.

Deposits are found in Burma (Myanmar), Cambodia, Sri Lanka, Thailand, as well as Australia, Brazil, Korea, Madagascar, Mozambique, Nigeria, and Tanzania.