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gemstone glossary

GEMSTONE GLOSSARY


alexandriteAlexandrite (Chrysoberyl)
Colour: Green in daylight, reddish purple in tungsten or candle light
Hardness: 8½ Mohs’ scale
Specific Gravity: 3.71 - 3.75
Refractive Index: 1.74 - 1.76
Chemical Composition: Beryllium aluminium oxide
Principal Sources: Brazil, Sri Lanka, Burma

amberAmber
Colour:White, yellow, orange, brown, black, red, sometimes with insect inclusions
Hardness: 2½ Mohs’ scale
Specific Gravity: 1.05 - 1.09
Refractive Index: 1.54
Chemical Composition: Fossilised tree resin from pine trees
Principal Sources: Baltic and North sea coasts, Pit Amber, Romania, Burma

amethystAmethyst (Quartz)
Colour: Transparent purple to pale lilac
Hardness: 7 Mohs’ scale
Specific Gravity: 2.65
Refractive Index: 1.54 - 1.55
Chemical Composition: Silicon dioxide
Principal Sources: Brazil,Africa,Australia

aquamarineAquamarine (Beryl)
Colour:Very pale to deep intense blue
Hardness: 7½ - 8 Mohs’ scale
Specific Gravity: 2.7 - 2.8
Refractive Index: 1.56 - 1.60
Chemical Composition: Beryllium aluminium silicate
Principal Sources: Brazil,Africa, Russia

bloodstoneBloodstone (Quartz)
Colour: Deep opaque green with red patches
Hardness: 7 Mohs’ scale
Specific Gravity: 2.65
Refractive Index: 1.54 - 1.55
Chemical Composition: Silicon dioxide
Principal Sources: Brazil,Africa

carnelianCarnelian (Quartz)
Colour: Reddish brown to yellowish red, orange
Hardness: 7 Mohs’ scale
Specific Gravity: 2.65
Refractive Index: 1.54 - 1.56
Chemical Composition: Silicon dioxide
Principal Sources: Brazil, Madagascar, India, Sri Lanka

citrineCitrine (Quartz)
Colour: Pale yellow to yellowish brown
Hardness: 7 Mohs’ scale
Specific Gravity: 2.65
Refractive Index: 1.54 - 1.55
Chemical Composition: Silicon dioxide
Principal Sources:Africa, Brazil

coralCoral
Colour: Red, pink, orange, white and black
Hardness: 3½ Mohs’ scale
Specific Gravity: 2.60 - 2.70
Refractive Index: 1.48
Chemical Composition: Calcium carbonate
Principal Sources: Mediterranean and islands around Japan

cubic-zirconiaCubic Zirconia
Colour: Colourless and various other colours
Hardness: 8½ Mohs’ scale
Specific Gravity: 5.6 - 6.0
Refractive Index: 2.17
Chemical Composition: Man-made diamond simulant

diamondDiamond
Colour: Colourless, but also found in other colours, the finest of which, are called fancy diamonds
Hardness: 10 Mohs’ scale
Specific Gravity: 3.52
Refractive Index: 2.42
Chemical Composition: Pure carbon
Principal Sources:Australia,Africa, China, Brazil, India, Russia, Canada
Graded by 4Cs - colour, clarity, cut and carat weight

emeraldEmerald (Beryl)
Colour: Green - the deeper richer colours are the most desired
Hardness: 7½ Mohs’ scale
Specific Gravity: 2.7 - 2.8
Refractive Index: 1.56 - 1.60
Chemical Composition: Beryllium aluminium silicate
Principal Sources: Columbia, Brazil, Pakistan, Russia

garnetGarnet
Colour: Red, green, yellow, orange, colourless
Hardness: 6½ - 7½ Mohs’ scale
Specific Gravity: 3.60 - 4.20
Refractive Index: 1.76 to 1.89 (depending on variety)
Chemical Composition:Various aluminium and/or calcium silicates
Principal Sources:Worldwide

jadeJadeite Jade
Colour:White, green, lilac, black, yellow and more
Hardness: 6½ - 7 Mohs’ scale
Specific Gravity: 3.30 - 3.38
Refractive Index: 1.66 approx
Chemical Composition: Sodium aluminium silicate
Principal Sources: Burma

jetJet
Colour: Black
Hardness: 3½ Mohs’ scale
Specific Gravity: 1.3 - 1.4
Refractive Index: 1.66 approx
Chemical Composition: Fossilised wood
Principal Sources: Germany, Spain, USA, Russia

lapis-lazuliLapis Lazuli
Colour: Blue,microcrystalline rock with flecks of iron pyrites
Hardness: 5½ Mohs’ scale
Specific Gravity: 2.7 - 2.9
Refractive Index: 1.50
Chemical Composition: Rock, consisting of lazurite, hauynite, calcite and pyrite
Principal Sources:Afghanistan, Russia, Chile

moonstoneMoonstone
Colour:Moonshine blue sheen from inside,white/colourless body
Hardness: 6 Mohs’ scale
Specific Gravity: 2.56 - 2.59
Refractive Index: 1.52 to 1.57
Chemical Composition:Orthoclase and plagioclase producing sheen
Principal Sources: Sri Lanka, India, Burma

nephrite-jade.jpgNephrite Jade
Colour: Green, yellowish, brown
Hardness: 6 - 6½ Mohs’ scale
Specific Gravity: 2.90 - 3.03
Refractive Index: 1.62 approx
Chemical Composition: Complex calcium silicate
Principal Sources:Worldwide

coralOpal
Colours:Many iridescent colours on pale to dark background, usually themore play of colour the better
Hardness: 5 - 6½ Mohs’ scale
Specific Gravity: 2.1
Refractive Index: 1.45
Chemical Composition: Hydrous silicon dioxide
Principal Sources:Australia, Brazil

pearlsPearl
Colours:White, black and pink blister
Hardness: 2½ - 3½ Mohs’ scale, compact structure
Specific Gravity: 2.60 - 2.78
Chemical Composition: Calcium carbonate, conchiolin (conchin) and water
Principal Sources: Central and SouthAmerica, Japan, Persian Gulf, Polynesia, China

peridotPeridot (Olivine)
Colour:Yellowish to deep olive green
Hardness: 6½ Mohs’ scale
Specific Gravity: 3.34
Refractive Index: 1.65 - 1.69
Chemical Composition:Magnesium iron silicate
Principal Sources: Zeberget (Isle of St. John) Red Sea, Burma, Brazil,Australia

rubyRuby (Corundum)
Colour:Various shades of red
Hardness: 9 Mohs’ scale
Specific Gravity: 3.99
Refractive Index: 1.76 - 1.77
Chemical Composition:Aluminium oxide
Principal Sources:Afghanistan,Africa, Burma,Thailand

sapphireSapphire (Corundum)
Colours:All colours except red
Hardness: 9 Mohs’ scale
Specific Gravity: 3.99
Refractive Index: 1.76 - 1.77
Chemical Composition:Aluminium oxide
Principal Sources:Africa, Burma, Sri Lanka,Thailand,Australia, India, Brazil

smoky quartzSmoky Quartz
Colour:Transparent brown to black
Hardness: 7 Mohs’ scale
Specific Gravity: 2.65
Refractive Index: 1.54 - 1.55
Chemical Composition: Silicon Dioxide
Principal Sources:Most are from Brazil but can be found worldwide

spinelSpinel
Colour: Colourless (rare), red, all shades of blue to violet, smoky pinks etc
Hardness: 8 Mohs’ scale
Specific Gravity: 3.58 - 3.61
Refractive Index: 1.72
Chemical Composition:Magnesium aluminium oxide
Principal Sources: Found in Burma, Sri Lanka,Thailand

tanzaniteTanzanite (Blue Zoisite)
Colour: Blue to violet
Hardness: 6½ Mohs’ scale
Specific Gravity: 3.35
Refractive Index: 1.69 - 1.70
Chemical Composition: Calcium aluminium silicate
Principle Sources:Tanzania

tigers eyeTiger’s Eye (Quartz)
Colour: Golden brown
Hardness: 7 Mohs’ scale
Specific Gravity: 2.65
Refractive Index: 1.54 - 1.55
Chemical Composition: Silicon Dioxide
Principal Sources: SouthAfrica

Topaz
Colour: Colourless, sherry, blue, pink, red, orange, yellow and green
Hardness: 8 Mohs’ scale
Specific Gravity: 3.53 - 3.56
Refractive Index: 1.61 - 1.64
Chemical Composition:Aluminium Fluo-silicate
Principal Sources: Brazil,Africa,Asia

tourmalineTourmaline
Colour:All colours
Hardness: 7-7½ Mohs’ scale
Specific Gravity: 3.01 - 3.11
Refractive Index: 1.62 - 1.66
Chemical Composition: Complex borosilicate of aluminium,magnesium and iron
Principal Sources:Africa, Brazil, Sri Lanka, Russia, USA

turquoiseTurquoise
Colour: Sky blue, blue-green, apple green
Hardness: 5½ - 6 Mohs’ scale
Specific Gravity: 2.60 - 2.90
Refractive Index: 1.63 approx
Chemical Composition: Hydrous copper aluminium phosphate
Principal Sources: Iran,Afghanistan, Israel

zirconZircon
Colour: Colourless, yellow, brown, orange, red, violet, blue, green
Hardness: 6½ - 7½ Mohs’ scale
Specific Gravity: 3.90 - 4.68
Refractive Index: 1.78 - 1.99
Chemical Composition: Zirconium Silicate
Principal Sources:Thailand, Sri Lanka,Australia, Cambodia

 

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