Gemstones A-Z with detailed gemstone descriptions
N.B.This stone is very sensitive to heat and care needs to be taken.
CITRINE
Citrine is a form of quartz with ferric iron impurities and is rarely found naturally. Origin of  name from the French word "citron" meaning lemon. Also called citrine quartz. Most commercial citrine is in fact heat treated amethyst or smoky quartz. Brazil is the leading producer of naturally mined citrine.
Colour: the different shades range from yellow, gold, orange brown shades of transparent  quartz.
Hardness:7
N.B. Citrine and Amethyst are the exact same minerals, the only difference is the level of oxidation of the iron contained in the mineral. As this can be done artificially  by heat  or irradiation a large majority of Citrine sold today is  heat treated amethyst. There are currently no scientific ways to determine if Citrine was changed artificially.
CORAL
Precious coral or red coral is the common name given to Corallium rubrum. The hard skeleton of red coral branches is made up of mostly calcium carbonate and is durable and intensely coloured. Coral    can be polished to a glassy shine. Usually deep water corals have light colour and shallow water corals have deep colour. Coral jewellery has been found in ancient Egyptian and prehistoric European burials and continues to be made to the present day. Due to its softness and opacity, coral is usually cut as a cabochon or used to make beads.
Hardness:3.5
CUBIC ZIRCONIA
Cubic zirconia or CZ is a synthetic variant of the mineral baddeleyite which is extremely rare in nature. It is the oxide of the metallic element zirconium, zirconium dioxide. It was first used in the Russian space program to serve as a window to photograph   through, it was not used in jewellery until 1969 when somebody decided to facet   the material. It is often used as a diamond simulant.   Cubic zirconia should not be confused with zircon, which is a rare naturally occurring gemstone.
Colour: By adding other minerals in the creative process CZ's can come in any colour as well as the colourless variety.
Hardness:8.25-8.75
N.B. Key features that distinguish  CZ  from diamond:
Cubic zirconias have more dispersion than diamonds so show more fire.
A CZ has a Mohs rating of 8.5-9 and Diamonds have a rating of 10.
A CZ is 1.7 times heavier than a diamond of equivalent size.
CZs are optically flawless whereas the majority of diamonds have inclusions or flaws
CZ has a refractive index of 2.176, compared to a diamond's 2.417.
CZ can be made in most cases entirely colourless: equivalent to a perfect "D" on diamond's colour grading scale but it is rare to find diamonds are truly colourless.
CZs are thermal insulators whilst diamonds are among the most efficient thermal conductors.
DIAMOND
Diamonds are a form of carbon. Origin of name:  From Greek for invincible. Please click here to go to our more comprehensive section on Diamonds.
Colour: it is rare to find diamonds are truly colourless.
Hardness: 10.00
COLOURED DIAMONDS
Diamonds come in all colours but these natural Fancy Colour Diamonds are rare and can be very expensive. One out of 10,000 normal diamonds is a fancy colour diamond. The colour of a fancy coloured diamond is measured differently to a normal diamonds. The grading scale is based on the intensity of the colour. The GIA fancy colour grading scale is: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep and Fancy Dark.
EMERALD
Emerald is a valuable Beryl that owes its colour to chromium or vanadium, which make it the bright green. Origin of name emerald is said to be a Sanskrit word  meaning green (Sanskrit is a classical language of India). Emeralds can have many inclusions and flaws so can be brittle and liable to break.The value of an emerald depends on cut, colour, clarity and carat. Clear stones with vibrant colour command the highest prices.  It is found in Brazil, Pakistan, Russia, East Africa, India, Madagascar and Columbia, at this point in time the best emeralds come from Colombia.
Colour: Emeralds come in many shades of green and bluish green.
Hardness: 7.5-8
N.B. Many emeralds are treated to hide surface-reaching breaks and improve transparency.
FIRE OPAL
Fire opal is a bright orange variety of opal .
It is primarily found in Mexico, so is often known   as Mexican fire opal. Fire opal was known to the Aztecs between about 1200 to   1519 AD
Colour:Fire opals are transparent to translucent opals with warm body colors yellow,   orange, orange-yellow or red.
Hardness:5.5- 6.5
GARNET
Garnets are nesosilicates. 0rigin of name: from ancient Greeks as colour reminded them of the pomegranate seed or granatum. Garnets do not show cleavage (the tendency of crystalline materials to split along definite planes, creating   smooth surfaces) so when they fracture under stress, sharp irregular pieces are formed. Because the chemical composition of garnet varies, the atomic bonds in some species are stronger than in others. The harder species are often used for abrasive purposes.  It is found in the regions of Kenya, Sri Lanka, Thailand, Brazil, India,   Madagascar, Canada, USA, Czech Republic and Spain.
Colour: virtually all colours
Hardness:6-7.5
IOLITE
Iolite is a blue silicate mineral that occurs as crystals or grains in igneous rocks, Origin of name: from the Greek ios, which means violet. Iolite changes   colours (pleochism) depending upon which angle it is viewed from and the gems are cut to take advantage of that.                      It is found in Sri Lanka, Burma, Australia's Northern Territory, Namibia, Brazil, Tanzania, Madagascar, Connecticut, and the Yellowknife area of the Northwest Territories of Canada.
Colour: Transparent, violet-blue, light blue, blue, rich blue-violet stone
Hardness 7.5
IVORY
Ivory is a hard, white, opaque substance that is the bulk of the teeth and tusks of animals such as the elephant, hippopotamus, walrus, mammoth and narwhal. Ivory had been used for thousands of years for tools, implements and weapons and for carving and jewellery. The 1990 Convention on International Trade in Endangered Species (CITES) put a  ban on international ivory sales to lessen the threat to endangered species by poaching. A species of hard nut sometimes called vegetable ivory or "tagua" is gaining popularity as a replacement for ivory.
JADE
The term "jade"refers to two different, yet similar semi-precious metamorphic mineral gemstones, Jadeite and Nephrite. Nephrite and jadeite are resistance to breakage and chipping  and due to their toughness they   made a superior weapons and tools for early man. Not until the 19th century that a French mineralogist determined that "jade" was in fact two different materials.  Nephrite is usually only green and creamy white, while jadeite can have the full range of jades colours.  Jade is mined in the regions of Canada, Australia, United States and Taiwan.
Hardness:6
JASPER
Jasper is microcrystalline quartz and is made from very small grains, it is a  semi-translucent to opaque. Jasper has been used for thousands of years   as tools and weapons during   prehistoric times and for ornaments and jewellery later. Origin of name from the Greek iaspis.   Jasper is commonly found in the regions of North Africa, Sicily, France, India,   Venezuela and Germany, USA etc.
Colour: dark green,yellow, brown, green, yellow, red and white.
Hardness: 6.5 to 7.5
JET
Jet is a  hard gem variety of Lignite. Jet is a type of brown coal, a fossilised wood of an ancient tree similar to our present  monkey puzzle trees and cypress trees. These trees flourished in the Jurassic period when the trees died and fell they were eventually washed into rivers and seas to lie at the bottom for millions of years. All the other sediment built up causing great pressure, which flattened the wood and together with chemical changes altered the wood to jet. Jet has been used in Jewellery since ancient times and Queen Victoria wore Whitby jet as part of her mourning dress making it very popular.
LAPIS LAZULI
Lapis lazuli is an opaque to translucent precious gemstone composed mainly of lazurite and calcite. Origin of name  from the Persian "lazhward", which was the name of a place in modern Turkestan known for its deposits of lapis lazuli (ï¿½stone of lazhwardï¿½).  The finest colour is intense blue, lightly dusted with small flecks of golden pyrite. Polished Lapis  can be made into jewellery. In the past it  was also ground and processed to make the pigment Ultramarine for tempera paint and oil paint.
Colour: Deep azure blue to light blue, bluish green
Hardness: 5.5-6
LARIMAR
Larimar is a semi-precious  blue variety of pectolite,   Sodium Calcium Silicate Hydroxide. It was discovered in the Bahamas and Dominican Republic in the 1970's. The name "Larimar" comes from a combination of Larissa and Mar and was given to   the stone by a Dominican who named the stone after his daughter Larissa and Mar,   the Spanish word for sea. Although pectolite is found in many locations, none have the unique blue of larimar. This blue color, distinct from that of other   pectolites, is the result of cobalt substitution for calcium.
Colour: pale blue to sky blue
Hardness: 5
MARCASITE
In jewellery, iron pyrite used as gem is improperly termed "marcasite" Origin of name from Arabic or Moorish for pyrite. Pyrite and Marcasite share the same exact chemical make up; however they both   differ in their interior structure." Marcasite" is frequently found in inexpensive silver jewellery and watches. It was fashionable and popular in Victorian and other times where it was often used to imitate diamonds. In better quality jewellery it is hand-set with grains or beads of metal from the setting being pushed over the edges of the stones." Marcasite" occurs world-wide and is easily found in the chalk near Dover,   Folkestone, and the French side of the English Channel.
Colour: metallic
Hardness:6-6.5
MOISSANITE
Naturally occurring Moissanite was discovered in 1905 by Dr. F.H. Moissan, a French chemist and Nobel Prize winner and was named after him. Natural moissanite is very rare and is limited to iron-nickel meteorites. Virtually all of the moissanite  sold in the world is synthetic. Synthetic moissanite is also known as silicon carbide after its chemistry (in industry moissanite is  known as the man-made abrasive Carborundum).  Moissanite is used as a diamond substitute  as it is transparent and hard  with a slightly higher refractive index than diamond.  Moissanite jewels   are cut to minimize their double refraction or birefringent effects. It is lighter and much more resistant to heat. This results in a stone of higher lustre, sharper facets and good resilience. Moissanite   remains undamaged by temperatures used to melt gold.
Colour:rarely clear to shades of very pale green.
Hardness:9.5
MOONSTONE
Moonstone is the best known gem variety of orthoclase feldspar. It is usually polished as a cabochon. Its importance as a gemstone arises because of adularescence, a floating light effect and sheen, compared to the   light of the moon. This phenomena results from alternating layers of two kinds of feldspar,which cause light to scatter. Moonstone specimens commonly exhibit chatoyancy (a mobile, wavering striped reflection), and sometimes display a strong   cat's eye.
Colour: most desirable colour of moonstone is blue, but it also occurs in grey, white, pink, green and brown.
Hardness: 6 to 6.5  
MYSTIC TOPAZ
Mystic topaz is a treated clear topaz, it is not found naturally. To create mystic topaz, natural, colourless topaz is coated with a thin layer of titanium. The coating is only microns thick and is applied to the stones pavilion, the underside angled portion that typically forms the bulk of the gem.   The specialized coating alters the stones natural refraction, creating rainbow colours, predominantly blues, greens, yellows, and small bursts of red shades.
N.B. this stone should be treated with care
ONYX
Onyx ia a chalcedony that occurs in bands of different colours. Onyx refers to a black and white banded variety of Agate and   brown varieties are named Sardonyx. It is composed of   relatively straight, parallel layers of different colours. This structure lends itself to cameo making.
It   is usually cut into cabochon, or into beads, and is also used for intaglios and   cameos. Some onyx is natural but much is produced by the staining of agate. It   is available in the regions of USA, Germany, Brazil, Mexico, India, and Africa.
Hardness: 7
OPAL
Opal is a  type of quartz. Origin of name: from Sanskrit (Sanskrit is a classical Indian language) upala = precious stone.  They are luminous and iridescent with inclusions of many colours. Opals show a play-of-colour (a shifting of spectral colours)Opals are found in the regions of Mexico, Brazil, USA, Japan, Honduras, Kenya, Czechoslovakia, Peru, Canada  but by far Australia is the main source of opals, almost ninety-five per cent of all fine opals come from the dry and remote outback deserts.
Colour:     White, black, red, orange, most of the full spectrum, colourless, iridescent. Very infrequently of a  singular colour.
Hardness: 5.5- 6.5
PEARL
Pearl is a smooth, lustrous, chiefly calcium   carbonate organic gemstones. Natural pearls are nearly 100% nacre, a protective mother of pearl coating that is secreted to protect the organism for a foreign body that has entered the shell. Natural or real pearls come mainly from oysters, although there are other   bi-valve molluscs which can produce them. Almost any species of bivalve or gastropod is capable of producing pearls. However, only a few species, such as the famous pearl oysters, can create pearls which are highly prized. Cultured pearls are produced by artificially introducing a foreign object into the fleshy part of oysters, which become coated with nacre in a similar manner to natural pearls. Imitation pearls, simulated pearls, have been produced for many   years.  Pearls are found in the regions of Japan, China, Tahiti, Australia, Indonesia,   Philippines, USA and Burma.
Colour: white or cream, but the colour   can vary  according to the natural colour of the nacre in the various   species of mollusc used. Can also be black or various   pastel shades. Pearls (especially freshwater pearls) can be dyed yellow, green, blue, brown, pink, purple, or black
Hardness: 3.5 to 4.0
N.B.To test if a pearl is natural, rub across your across the edge of your teeth; real pearl feels rough, simulated feel smooth.
PERIDOT
Is the gem quality variety of the mineral olivine. Origin of name either the Arabic word faridat meaning "gem" or the French word peritot meaning "unclear". Peridot is one of the few gem stones that come in only one colour. The depth of green depends on how much iron is contained in the crystal structure. It is found in the USA, Myanmar, Egypt, China, Sri Lanka and Pakistan.
Colour: varies from yellow-green to olive to brownish green.
Hardness: 6.5 - 7
QUARTZ
Quartz is a crystalline rock or mineral composed of silicon dioxide. Quartz  is the second most common mineral in the Earth's continental crust and found in all types of geological environment. There are 49 variety's, a number of which are gemstones, some of which are very beautiful and very rare. Origin of name from Saxon word Querkluftertz = cross-vein ore.
Colour: colourless, white, gray, yellow to brown to black, violet, pink
Hardness: 7
RUBY
Ruby is the red variety of the mineral called Corundum which is composed of aluminium oxide (any other colour of corundrum is a sapphire, see below). The red colour is caused mainly by chromium and titanium. It is natural for  rubies to have imperfections in them, including colour impurities and inclusions of rutile needles known as "silk. Origin of name comes from ruber, Latin for red. Some rubies show a 3-point or 6-point star or asterism. These rubies are cut into cabochons to display this effect. Natural occurring rubies are very rare and extremely rare in large sizes   over 3 carats. They can be found in many regions around the world from India, to East Africa,   to South America, the Hindu Kush and a few deposits in the United   States.
Colour: pinkish red or deep, rich red colour
Hardness: 9
N.B. Almost all rubies today are treated in some form (of which heat treatment is the   most common practice) and rubies which are completely untreated and still of  excellent quality command a large premium.        Improvements used include colour alteration, improving transparency by   dissolving rutile inclusions, healing of fractures (cracks) or even completely   filling them.
SAPPHIRE
Sapphire is any colour of the mineral corundum other than red, those are called ruby, (see above) corundum is composed of aluminium oxide. Sapphires tend to be translucent or transparent and have high amounts of   refraction.  The most desirable sapphires are generally those with an intense blue colour with plenty of sparkle and life. Various shades of blue  result from titanium and iron substitutions in the aluminium oxide crystal lattice. Some sapphires show a 3-point or 6-point star or asterism. These sapphires are cut into cabochons to display this effect. They can be found in Brazil, Tanzania, Sri   Lanka, Kashmir, Thailand, Madagascar and Australia. 
Colour: Shades of blue, other colours- padparadscha(salmon pink), pink and purple, orange and yellow, green, and colorless and black. Each category has its own color range.
Hardness: 9
COLOURED SAPPHIRES
Sapphires are mainly known for their shades of blues, but they come in an assortment of colours.
Colour: all colours across the spectrum including white and black.
Hardness: 9
N.B. It should be noted that many Sapphires can be treated to enhance  or change their colour.  They are heated or irradiated to produce stronger colours such as greens, yellows or even blues. While the colour of Sapphires can be changed by intense heat and radiation, it is stable for daily wear jewellery.
SHELLS
Shells are organic minerals composed of calcium carbonate . Throughout the history shells of many types and from many different kinds of animals have been popular as human adornments.  They are often used whole and drilled so that they can be threaded. The intricate design and varying colour patterns of shells is mainly dependent on the diet of the animal the shell covers. Mother of pearl or nacre is created by  molluscs such as oysters and abalones  secreting   a substances that consist of calcium carbonate. Nacre is continually deposited onto the inner surface of the animal's shell creating the iridescent nacreous layer or mother of pearl. This is done both as a means to thicken, strengthen and smooth the inner surface of the shell. Mother of pearl has been used as decoration from buttons to inlays in furniture, jewellery and much more for thousands of years. Mother of Pearl can be found in many regions including Japan, Australia, Europe   and the United States.
Colour:
Hardness: 
NATURAL SPINEL
Spinels are composed of magnesium aluminium oxide. Most Spinel is formed due to intense heat from volcanic activity or hydrothermal   underwater streams. Origin of name: from Latin spinella meaning little thorn, after crystal shape. Spinels  next to ruby and the rare red diamond, is the most expensive of all red   gems. With a hardness of 8 and no cleavage planes, natural spinel is a tough and durable   gemstone suitable for any kind of jewellery. Unfortunately most Spinel that is sold commercially is synthetic. Sri Lanka, Brazil, Thailand, and United States are most notable sources of natural spinel.
Colour: cobalt blue, red to blue to mauve. Dark green, brown, blackgreen, pink,  deep pink with an orange tinge.
Hardness:8
TANZANITE
Tanzanite is part of the zoisite mineral species and is only found in East   Africa. Discovered in 1967 in the Umba Valley near the Usambara Mts. in Tanzania. Tanzanite  may be colourless, yellow-green, brown, or blue to violet when found; the crystals are heat treated to enhance their colour.
Colour:Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and sage-green depending on crystal orientation. (Trichroism is the  property possessed by certain minerals of exhibiting three different colours when viewed from three different directions under white lights. However, most tanzanite is subjected to artificial heat treatment to improve its colour and this significantly subdues its trichroism.
Hardness: 6.5
N.B: Tanzanite is a brittle stone and although it can be worn daily, care should be taken to protect it from knocks, pressure and extreme temperature changes. Do not use a home ultrasonic to clean jewellery with tanzanite
TOPAZ
Topaz is a fluorosilicate and can contain trace elements  that cause   different colours within the Topaz. Origin of name: from Greek Topazion, a Red Sea Island often covered in mist. Topaz wasn't really known about before the classical era, in the Middle Ages the name topaz was used to refer to any yellow gemstone. Deposits of topaz are found in the regions of Russia, Siberia, Brazil, Sri   Lanka, Africa and China, Japan, Pakistan, Myanmar, Nigeria, Australia, Mexico,   and in the United States.
Colour: Varies in a broad range of: yellow, blue, pink, peach, gold, green, red, and   brown.
Hardness: 8
N.B. Topaz is often heated to change or enhance it's colour.
TOURMALINE
Tourmaline is one on the most complex gemstones of the silicate group and there are 10 different varieties created by the  dozen or more elements they contain. Origin of name: from Sinhalese turamali = stone of mixed colours. There are Tourmalines, which change the colour from daylight to artificial light and others display chattoyance(a mobile, wavering striped reflection).Tourmaline is found in Africa, Brazil, Madagascar, Mexico, Myanmar, Namibia, Sri   Lanka and USA.
Colour: depending on the variety green, red to pink, light to dark blue, colourless, purple , neon blue, brown, black, red to green and green to red.
Hardness:7-7.5
N.B. Tourmaline may be heated to enhance it's colour.
TIGERS EYE
Tigers Eye is mainly composed of silicon dioxide, it is a  form of quartz that acquires fine golden lustre when polished. Origin of name: the stone resembles the eye of a tiger. Tiger's eye  is a semi precious stone with a rich yellow   and golden brown stripes that display chattoyance(a mobile, wavering striped reflection). Tigers eye is found in regions of South Africa and Western Australia.
TURQUIOSE
Turquoise is composed of aluminium phosphate and copper. Origin of name: from French for Turkish stone as in ancient days it was transported through Turkey. It was very popular during the days of Ancient Egypt and Ancient Persia and known to man since at least 6,000 BC. Delicate veining, caused by impurities, is desired by some collectors as proof   of a natural stone. Turquoise is found in the regions of Iran, southwestern United States, Africa, Australia, Tibet, China, Siberia and Europe.
Colour: Blue, blue-green, green
Hardness: 5-6
NATURAL ZIRCON
Zircon is zirconium silicate, belonging   to the group of nesosilicates. Origin of name: from Arabic zarqun and Persian zar = gold, gun = colour. Zircon is a natural forming mineral and it is not related to the synthetic diamond substitute Cubic Zirconium which is created in a laboratory. Zircon has a high refractive index and can be used to imitate diamonds. It is found in Australia, India, Brazil, and Florida, Cambodia, France, Myanmar, Thailand, Nigeria and Tanzania. Zircons found at Jack Hills in the Yilgarn Craton Western Australia are the oldest minerals found so far with an age of 4.404 billion years.
Colour: Zircon can come in red, brown, yellow, green, black or colourless. The colour of zircons below gem quality can be changed by heat treatment. Depending on the amount of heat applied, colourless, blue and golden-yellow zircons can be made.
Hardness: 7.5