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.
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.
Alexandrite is a variety of chrysoberyl that displays a colour change depending on light conditions and the angle it is view from (pleochroism).The ideal colour change would be fine emerald green to fine purplish red, but this is rare and expensive. Alexandrite was discovered in the Ural Mountains of Russia in the 1830's, and named after tsaravitch Alexander, the future tsar. That area was mined for over 60 years and still today Russian Alexandrite is considered the best quality. Today, small quantities of Alexandrite are mined in Brazil, Sri Lanka, India, Myanmar, Tanzania and Zimbabwe.
Colour:Green in daylight and red-violet in incandescent light.
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.
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.
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.
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.
Amethyst is a transparent purple quartz. Origin of name from the Greek -amethystos- "not drunken". Amethyst was considered to be a strong antidote against drunkenness. Greek legend tells the story of a maiden Amethystos who was pursued a drunken god called Dionysus. She prayed to the goddess Artemis to remain chaste. The goddess granted her prayer, transforming her into a white stone. Filled with remorse Dionysus cried tears of wine over the stone turning it purple.
Different localities can produce a unique amethyst to that particular region or even to that particular mine. It is mined in Brazil, Uruguay, Bolivia and Argentina, Zambia, Namibia and other African countries. Very dark amethyst, mostly in small sizes, is also mined in Australia.
Colour:the colour range varies from pale lilac to deep purple.
Aquamarine belongs to the gemstone family of Beryls. Origin of name Latin "aqua"meaning water and "mar"sea. Legend has it that Mermaids tails were made of aquamarine. Aquamarine is usually free of inclusions and possesses a superior brilliance. The more intense the colour of an Aquamarine, the higher its value.The principle supply of aquamarine stones comes from Brazil, Russia, Afghanistan, India and Pakistan
Colour:pale blue to light greenish
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
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
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.
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.
N.B. Topaz is often heated to change or enhance it's colour.