FAQ - Precious and Semi Precious Stones
Actinolite Cat's Eye
Actinolite is a rare translucent variety of chatoyant actinolite. It is an amphibole silicate that is sometimes mistakenly called 'cat's eye jade'.
Agate is a form of chalcedony quartz that forms in concentric layers in a remarkable variety of colours and textures.
Agate Geodes are a form of chalcedony quartz that forms in concentric layers in a remarkable variety of colours and textures within rock cavities or vugs with internal crystal formations.
Alexandrite is one of the rarest of all coloured gemstones and is famed for its colour change from green in daylight to red under incandescent light.
Almandine garnet the most common garnet, is dark-brownish or purplish-red. Garnet is very popular for its excellent hardness and brilliance.
Amazonite is a gemstone variety of green microcline, a feldspar mineral. It is named after the Amazon River in Brazil, although no deposits have been found there.
Amber, the fossilized, hardened resin of the pine tree, is one of the few gemstones of organic origin. Most amber is found in the Baltic, where it formed about 50 million years ago.
Amethyst is the most precious gemstone within the quartz group. Amethyst ranges in colour from pale lilac to deep reddish-purple.
Amethyst Geode is a trade name for violet quartz that forms within rock cavities and is often traded under names such crystal clustres or crystal plates.
Ametrine is a form of quartz that occurs in bands of yellow and purple, a combination of the colours of amethyst and citrine.
Ammolite is a rare gemstone of organic origin that is fairly new to the market, with commercial mining beginning only in 1981.
Andalusite is a strongly pleochroic gem, which means that it can display different colours when viewed from different angles.
Supplies of andesine-labradorite are quite recent, with the mineral found in a range of colours, including red, yellow, champagne and green.
Apatite, a stone seldom found in jewellery stores, is beloved by collectors for its many different colours and forms.
Aquamarine is best known for its breathtaking range of blue colours and belongs to the same family as emerald (beryl). Aquamarine is coloured by trace amounts of iron.
Aventurine is a type of green quartz often used for carvings and cabochons.
Axinite is a group of brown to violet-brown or reddish-brown minerals that sometimes occur in gem quality. Axinite is distinctive for its strong vitreous lustre.
A new high tech enhancement process using thin film deposition has created this new-look topaz.
Beryl is one of the most important gem minerals. The most famous beryl is emerald, but other beryl varieties include aquamarine, heliodor and morganite.
Black Opal is the most valuable opal variety. Its dark body colour can range from dark to black and acts as the base for the spectrum of colours it can exhibit.
Bloodstone, also known as heliotrope, is a green gemstone dotted with bright red spots of iron oxide.
Boulder opal is the second most prized form of opal, after black opal. The name is derived from the fact that boulder opal is found embedded in ironstone boulders.
Pure calcium carbonate is colourless, but calcite is often coloured by various impurities, including iron, magnesium, manganese, zinc or cobalt.
Carnelian is a brownish red to orange variety of chalcedony quartz, coloured by trace amounts of iron. Darker colours (red-brown to brown) are often referred to by the name sard.
Cassiterite is one of the densest gem materials known. It also has a very high refractive index, higher than zircon, sphene and demantoid garnet.
Cat's Eye Apatite
Chatoyancy (the cat's eye effect) in cat's eye apatite is the reflection of light by parallel fibres, needles, or channels, which resemble the slit eye of a cat.
Cat's Eye Aquamarine
Aquamarine is best known for its breathtaking range of blue colours and belongs to the same family as emerald. Cat's eye aquamarine is quite rare.
Cat's Eye Diaspore
Diaspore, sometimes marketed under the name zultanite, is a colour change gem from Turkey. Cat's eye diaspore is fairly rare.
Cat's Eye Scapolite
Scapolite is a sodium calcium aluminium silicate with a hardness of 5.5 to 6 on the Mohs scale. It is named after the Greek word for "stick", since its crystals grow in columns.
Cat's Eye Tourmaline
Tourmaline with tiny parallel inclusions sometimes displays a strong cat's eye effect when polished.
Chalcedony is the fine-grained variety of the silica mineral quartz. It has a waxy lustre and appears in a great variety of colours.
Charoite is a new gem on the market, first appearing in 1978. It is found only in one location in Siberia, Russia. The swirling shapes of lavender and violet are quite unique.
Chrome diopside is coloured by chromium and displays a rich forest green that has similarities with tsavorite garnet and chrome tourmaline.
Chrome tourmaline is a distinct variety of tourmaline coloured by chromium. It is sometimes referred to as chrome dravite and is known for its rich forest green colour.
Faceted chrysoberyl is a beautiful gem which is not as well known as it deserves. Apart from the very good hardness (8.5 on the Mohs scale), it has excellent lustre.
Chrysoberyl Cat's Eye
The most famous and valuable cat's eye gemstone is chrysoberyl cat's eye. It is valued for its excellent hardness (8.5) and sharp cat's eye.
Chrysocolla is hydrous copper silicate. Often confused with turquoise, chrysocolla is found in unusual multicolour combinations as well as blue or green.
Chrysoprase is a gemstone variety of chalcedony or cryptocrystalline quartz, coloured by trace amounts of nickel. Its colour varies from apple-green to deep green.
Named after the French word for lemon, citrine is yellow, gold or orange-brown transparent quartz.
Clinohumite is a rare mineral and an especially rare gemstone. Only three sources of gem-quality clinohumite material are known; in Tajikistan, Siberia and Tanzania.
Diaspore, sometimes marketed under the name zultanite or csarite, is a natural colour change gemstone mined from Turkey, which was recently introduced to the international market.
Colour-change garnet is a mix of spessartite and pyrope garnet. This garnet presents a colour change from brownish in daylight to rose pink in incandescent light.
Some rare sapphires exhibit a colour change under varying lighting conditions. Colour change sapphires are typically blue in natural light and purple under incandescent light.
Precious coral is a species of coral that grows in rocky sea bottoms. Coral exhibits a range of warm reddish-pink colours ranging from salmon pink to deep-red.
Danburite gets its name from Danbury, Connecticut, where it was first discovered in 1839. It is quite hard, with a rating of 7 to 7.5 on the Mohs scale.
Demantoid garnet is the rarest and most valuable of the garnets. Found in green to emerald green, demantoid garnet is scarce and is typically only seen in small sizes.
Dendritic agate is a whitish-grey or colourless chalcedony with fern-like inclusions known as dendrites. The inclusions look like plant material, but they are actually iron or manganese.
Diamond, the hardest known natural material, is a transparent carbon crystal. Diamond is famed not only for its superb hardness, but also for its high refractive index and dispersion.
Dumortierite quartz is an unusual quartz that is intergrown with the mineral dumortierite. The inclusions of dumortierite give it a deep blue colour that is unique in the world of quartz.
Emerald is the most precious stone in the beryl group. The wonderful green colour of emerald is unparalleled in the gem world.
Enstatite is a rare gemstone that belongs to the pyroxene group of minerals. It is typically brown-green with a vitreous lustre and is a collector's gem.
Fire agate is a type of opaque, limonite-bearing chalcedony with an iridescence caused by the diffraction of light in its layered structure.
Fire opal is an unusual variety of opal from Mexico, which can be yellow, orange or orange-red. Some fire opal gemstones are clear enough for facets.
Fluorite is a mineral with a veritable plethora of brilliant colours that include purple, blue, green, yellow, colourless, brown, pink and orange.
Fossil coral is a decorative material that is formed when ancient coral is gradually replaced with agate. The proper name for this material is agatized coral.
A recent discovery (1966), gaspeite is a very rare nickel carbonate mineral named after the place in Eastern Canada where it was first described.
The colourless precious beryl is known as goshenite. It is named after the small town of Goshen in Western Massachusetts where it was first described.
Grandidierite is a rare greenish-blue gemstone named after Alfred Grandidier. It is often listed as one of the top 10 rarest gems in the world.
Grossularite (or grossular) garnet is a calcium-aluminium garnet. The name grossular is derived from the botanical name for the gooseberry, grossularia.
Hackmanite exhibits an unusual phenomenon known as reversible photochromism, where a mineral changes colour when exposed to sunlight.
Hambergite is one of the lesser-known gemstones. It is usually nearly colourless, with the vitreous lustre of glass when cut. It is quite a hard material, with a hardness of 7.5.
Hematite is iron oxide that is typically blackish-grey. When highly polished it can sometimes look like silver. Hematite is a remarkably dense material.
Hemimorphite is usually found in aggregate form with blue and white bands, or mixed with a dark matrix.
Hessonite is an orange-brown variety of garnet coloured by traces of manganese and iron. It is sometimes known as cinammon stone.
Hiddenite is a form of spodumene containing chromium. The green colour varies from a yellowish to a bluish-green.
Howlite is an interesting greyish-white mineral that is sometimes referred to as white turquoise because of its distinctive veining.
Idocrase is also known as vesuvianite, since it was originally found on Mt. Vesuvias. The colour is normally green, but it can also be brown, yellow, blue or purple.
The most sought after of all natural topaz is called imperial topaz. Its rich golden colour with reddish and orange overtones is generally not enhanced by any kind of treatment.
Pleochroism is very pronounced in iolite and is seen as three different colour shades in the same stone; violet, yellow-grey and blue.
Jadeite is found in most colours, including pure white, pink, brown, red, orange, violet, blue, black and a range of greens.
Jasper is usually considered a type of chalcedony, however, scientists put it in a group by itself because of its grainy structure.
Kornerupine is a rare transparent to translucent, typically brownish-green collector's gem. It was named after Danish naturalist, artist and explorer, Andreas Nikolaus Kornerup.
Kunzite is the pale pink-violet to light-violet species of the mineral spodumene. Kunzite is named in honour of the mineralogist George F. Kunz.
Kyanite is a layered crystal with a vitreous to almost pearly lustre that is usually found in a sapphire-like blue colour.
Labradorite is a member of the plagioclase feldspar group and displays a distinctive schiller in lustrous metallic tints.
Lapis lazuli has been used for thousands of years in jewellery and ornamental objects. The unique deep blue colour has never lost its attraction.
The blue variety of pectolite has become known as Larimar. A very rare mineral, it has only been found in the Dominican Republic, where it was first discovered in 1974.
Lepidolite is a lilac-grey or rose-coloured lithium-bearing mineral of the mica group. It is one of the major sources of the rare alkali metals rubidium and caesium.
Malachite is copper carbonate with distinctive green veining. Though not a particularly hard stone, it takes an excellent polish.
Mali Garnet is one of the hybrid garnets, a mixture of grossular and andradite garnets. It gets its name from the African country where it was first discovered.
Maw-sit-sit is an unusual gemstone often classified as a member of the jade family. It was first discovered in 1963 and was named after a village in North western Burma.
Melanite is the black variety of the rare andradite garnet. It is sometimes known as titanian andradite.
Moldavite is a bottle-green to brown-green gemstone belonging to the tektite group. It is formed from condensed rock vapors after a meteorite impact.
Moonstone is a unique stone that reflects light in a distinctive shimmering phenomenon known as adularescence.
The pink form of beryl was named morganite, after the American banker and collector J.P. Morgan. A soft pink to violet, morganite belongs to the same family as emerald.
Moss opal is a milky white opal with unique inclusions of green hornblende in moss-like patterns.
Mystic quartz is the product of a new high tech enhancement process, whereby a coating is applied to colourless quartz.
Mother of Pearl
Mother of Pearl is an organic gemstone that comes from the inside of some mollusk shells. Mother-of-pearl is made from nacre, which is mainly calcium carbonate.
Colourful mystic topaz is the product of a high tech enhancement process that is stable and permanent.
Nuummite is an opaque metamorphic rock with an iridescent play of colour. Its chief constituent minerals are gedrite and anthophyllite.
Obsidian is naturally occurring volcanic glass. It is formed when felsic lava extruded from a volcano cools without crystal growth.
Onyx is the black form of chalcedony, a cryptocrystalline form of quartz.
More than any other gem, each opal is unique. No other stone has such rich and varied folklore. Opals are also the most delicate gems commonly worn.
An opal doublet consists of a slice of natural opal glued to a black backing, which causes the colour to become more vibrant.
Orthoclase is a transparent yellow feldspar resembling citrine quartz or yellow beryl, found primarily in Madagascar.
Paraiba tourmaline is a rare copper-bearing gem with a vivid neon blue colour. First found in Brazil in 1989, similar material has since been found in Africa.
Peanut wood is a variety of petrified wood, where the shape and structure of the wood is pre- served when the original organic material is replaced by quartz.
Pearls are products of bivalve mollusks (mainly oysters and mussels). They are built up of nacre, which is mainly calcium carbonate in the form of aragonite crystals.
Peridot belongs to the forsterite-fayalite mineral series. It is an idiochromatic gem, meaning its colour comes from the basic chemical composition of the mineral itself, rather than impurities.
Pietersite is a breccia aggregate of hawk's eye and tiger's eye, with swirling colours of blue, rusty red, gold and brown.
Prehnite, a form of calcium aluminium silicate, has a vitreous to pearly lustre. Affordably priced for its size, prehnite makes distinctive and interesting jewellery.
Pyrope garnet is the most famous of the red garnets. Its dark, blood red colour often resembles the colour of ruby.
Quartz is one of the most common minerals on Earth and is well known in the gemstone world in its many forms including amethyst, citrine and ametrine.
Quartz Cat's Eye
Quartz cat's eye is quartz in which inclusions of rutile create chatoyancy (the cat's eye effect). Usually found in white, green, yellow or brown.
A combination of orthoclase and albite arranged in layers cause the lovely sheen. Despite the name, rainbow moonstone is actually a variety of labradorite with a multicoloured adularescence.
Rainbow pyrite is a recent find from Russia. The material comes in the form of druzy - a layer of miniature pyrite crystals coating a matrix.
Rhodochrosite is usually found in an aggregate form with alternating light and dark stripes in zigzag bands.
Rhodolite garnet is the name applied to a mixture of pyrope and almandite. Rhodolite tends to be lighter in colour than most other kinds of red garnet.
Rhodonite is a manganese iron magnesium calcium silicate, and a member of the pyroxenoid group of minerals.
The unique soft pink colour of rose quartz is thought to be derived from tiny traces of titanium. Rose quartz crystals tend to be cloudy, which deepens its colour.
Vivid pink to red tourmaline, often with a violet tinge, is known as rubellite. It is one of the most valuable tourmaline colours.
Ruby is the red variety of corundum, the 2nd hardest substance on the Mohs scale, with a rating of 9. It is the combination of hardness and rich colour that makes fine ruby so valuable.
Ruby-in-fuchsite is a natural combination of ruby and fuchsite in the same specimen. It is an interesting and colourful stone, with blue to emerald-green fuchsite and pink, purple or red ruby inclusions.
Ruby-zoisite is the natural combination of ruby and zoisite crystals in a single specimen. It is often used for carvings.
Rutile quartz is clear or smoky quartz with inclusions of rutile crystals.
Rutile topaz is colourless topaz with inclusions that look like rutile crystals. But the inclusions are actually thin channels of limonite staining.
Sapphire, with its excellent hardness, second only to diamond, is one of the four traditional precious gemstones.
As a gemstone scapolite is not well known, but it can be a very attractive stone. Its colour, which is usually a vibrant yellow, orange, pink or violet, is its best feature.
Seraphinite is a trade name for a particular form of clinochlore. The dark-green colour of seraphinite is enhanced by a silvery and feathery shimmer caused by mica inclusions.
Serpentine is a type of green magnesium silicate aggregate. It is used as a decorative stone or for carvings.
Sillimanite Cat's Eye
Sillimanite is a type of aluminium silicate that is related to both andalusite and kyanite. In fact, these three minerals share the same chemical composition but have different crystal structures.
Smithsonite is one of two zinc-containing minerals discovered by the British mineralogist James Smithson. The zinc silicate was named smithsonite in his honour.
Smoky quartz is fast becoming a designer favourite for its earthy tone and tribal look. It is one of the few gemstones that is grey or brown.
Obsidian is a naturally occurring volcanic glass. In some stones, the inclusion of white crystals of cristobalite produce a blotchy pattern, known as snowflake obsidian.
The mineral sodalite gets its name from its sodium content. As a gemstone, sodalite is usually blue, often with a violet tint, and frequently contains white veins of calcite.
The most valuable spessartite garnets display a bright, orange-red. The best specimens come from Namibia.
Sphalerite is a rare collector's gem which has exceptional dispersion (also known as fire). In fact its dispersion rating is three times as high as that for diamond.
Sphene is a brilliant yellowish-green, green or brown gemstone of high lustre, unique colour shades and, with brilliant cut, an intense fire.
Due to its excellent hardness and clarity, spinel is an excellent gemstone for all types of jewellery. Spinel is never treated in any way.
Spodumene is a relatively new mineral to science, with gem varieties discovered only in the last 120 years. Spodumene occurs in white, grey, pink, lilac and green.
Diopside is best known for the vivid green chrome diopside, but the black diopside exhibiting asterism (also known as the star effect) is also important.
Star garnet is a rare and unusual garnet, found only in Idado in the USA and India. It displays a four-rayed star due to aligned inclusions of rutile.
Star Lemon Quartz
Star lemon quartz is a lemon-yellow variety of quartz that displays asterism (the star effect).
Moonstone is a combination of orthoclase and albite arranged in layers which cause the lovely sheen. Star moonstone exhibits a stunning four-rayed star effect.
Star Rose Quartz
Rose quartz displaying asterism or the star effect is rare. The unique soft pink colour of rose quartz is thought to be caused by tiny traces of titanium.
Star ruby is a ruby that displays asterism, a six-rayed star that shimmers over the surface of the stone when it is moved.
Star sapphire is a sapphire that contains unusual tiny needle-like inclusions. These needles produce a phenomenon called asterism.
Sunstone is plagioclase feldspar with a unique glitter from platelets of hematite. Typicaly it has a red glitter, and more rarely a blue or green glitter. Star sunstones are known but rare.
Quartz with red inclusions of lepidocrosite, hematite or goethite is often sold under the name strawberry quartz.
Sugilite is an obscure and quite rare mineral named after the Japanese geologist, Ken-ichi Sugi, who discovered it in 1944.
Sunstone is a type of plagioclase feldspar that exhibits a spangled appearance, due to reflections of red hematite.
Tanzanite is a variety of zoisite. Colours of tanzanite include blue, purple and green. The highly coveted colour is deep blue, which has a purple pleochroism.
Tashmarine diopside is a brilliant yellow-green diopside from a recent discovery in Tajikistan, Uzbekistan and Western China.
Tiger's eye is a type of opaque macro crystalline quartz with a fibrous structure. It typically displays chatoyant stripes, because structural fibres are crooked or bent.
Tiger's Eye Matrix
Tiger's eye matrix is the name given to tiger's eye that is cut and finished with some of its host rock intact.
Topaz is an important gem due to its hardness and high refractive index. Topaz comes in many colours and blue topaz is especially popular.
Tremolite is a rare gemstone sometimes known as 'hexagonite' or 'tremolite-hexagonite'.
One of the most versatile of gems, tourmaline is found in every colour. It can show every tone from pastel to dark, and can display various colours in the same stone.
The green species of garnet known as tsavorite was discovered in 1967 by British geologist Campbell R. Bridges in the bush along the frontier between Kenya and Tanzania.
Turquoise, the blue cousin of lapis lazuli, has been known and valued for thousands of years. The early mines in Sinai, Egypt, were already worked out in 2000 B.C.
Variscite is a relatively rare type of phosphate mineral. High quality specimens are used as gemstones and for carvings. Variscite is coloured by traces of chromium.
Verdite is light to dark-green serpentine rock that is often spotted or variegated. Most specimens come from South Africa and Zimbabwe.
Zircon has great brilliance and intensive fire, due to its high refractive index and strong dispersion.