Know About Your Gemstones :
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
WHITE 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
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.
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.
AMETHYST

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.
Hardness:
 7
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.
CATS EYE

Cat’s Eye is a mineral oxide which comes from the family of Chrysoberyl that is a Beryllium Aluminate by origin. This gemstone is also known by its scientific name of Cymophane. It is a translucent yellow chatoyant Chrysoberyl which has got its name from two ancient Greek words “Chryso” which stands for “Golden” and “Beryl” which stands for “Green”, together amalgamated as “Green Colored Beryl”. A Cat’s Eye is known for its distinct feature called Chatoyancy in which it shows a silky band of light green light which runs across the gemstone. Further, this phenomenon is also called as Milk and Honey Effect as a sharp milky ray passes through a honey colored background of the gemstone. 
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.
HESSONITE

Hessonite is a gem quality variety of grossularite (grossular) garnet, the calcium-aluminum silicate member of the garnet species. While most varieties of grossularite are green, hessonite is known for its characteristic honey-yellow to brown-red 'cinnamon' color, though it can occur in other colors as well. It is referred to as the 'cinnamon stone' or the 'kaneel stone' in reference to its distinct color. Other types of grossular garnets include the more common green grossularite, chromium-rich tsavorite, the rare hydrogrossular garnet and the rare leuco garnet (colorless).

Hessonite is an extremely important stone in Vedic astrology and like other garnets, it may also be worn as one of the traditional birthstones for the month of January. For many years, gems that were thought to be zircon were discovered to be hessonite. The name, 'hessonite', was derived from the Greek word 'hesson', meaning 'inferior' - in reference to the fact that hessonite has a density and hardness lower than that of most other forms of garnet
BLUE 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.
AQUAMARINE

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
Hardness: 7.5-8
IOLITE

Also known as Cordierite and water sapphire is usually a blue to violet colored gemstone - is a pleochroic gem meaning that when viewed from different orientations, it displays different colors. Metaphysical properties include: stimulation of the third eye, enhancement of your inner knowing; helps one to eliminate debt by accepting responsibility which leads to successful management of money; has been a stone worn by Shamans in the past to insure accuracy of visions; also can aid the elimination of disharmony in relationships.
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 (“stone of lazhward”). 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
MALACHITE

Malachite is believed to be a strong protector of children. It is said to protect the wearer from accidents and protects travelers. Malachite has been used to aid success in business and protect against undesirable business associations. It is a stone of balance in relationships.

Malachite is always green, usually in banded tones varying from very dark green to a mellow green. Most malachite comes from Zaire, Chile and Australia.
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  
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
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
NAVRATAN

This is the best kind of remedial for all problems ever found by ancient Indian Astrology. Nine kinds of precious gemstones combined in one locket according to ancient Indian culture to wipe away all your problems in job, marriage, family life, foreign travel, business and health. The persons facing unusual legal problems or under the machination of enemies, recover easily. These are highly praised in Ramayana and other Occult Texts of India for its amazing abilities to destroy all difficulties and diseases. It gives its wearer great fortune in a short period. These elegant Rings, Lockets and Bracelets hold Ruby (Sun), Blue Sapphire (Saturn) and Yellow Sapphire (Jupiter), Diamonds (Venus), Emeralds (Mercury), Cats-Eye (Ketu), Red Coral (Mars), Pearl (Moon) and Gomed (Rahu).
BLUE 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. 
Hardness: 9
YELLOW 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. 
Hardness: 9
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