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Precious stones such as diamonds, emeralds, rubies, and sapphires are distinguished from semi-precious stones by their hardness, brilliance, colour and clarity. The intrinsic value of a stone is determined by three factors; rarity, size and esthetics. Gemologists rate hardness on a scale of 1-10, with stones rated at 9 or 10 they would be classified as precious. Of this category diamonds are the hardest and most valuable. The most sought after diamonds are flawless meaning free of cracks, chips, and bubbles. They are either pink, blue, green, or colourless. They are certainly prized for their rarity. You'll notice most diamonds display a slight brown or yellow tinge. These stones are cut and ground to produce facets and refract light and flash prismatic colours.
Emeralds are very rare and valuable. They are often flawed and of variable quality. Ranging from pale to dark green, the darker being the most valuable particularly when displaying brilliance and clarity. Rubies like emeralds and sapphires are a variety of the hard mineral corundum. The are generally red and the best examples being flawless and dark blood-red with a strong fluorescence. The best sapphires come from Kashmir ranging from bright blue to dark blue.
Information on Semi-Precious Stones
Semi-precious stones generally have a have a hardness rating of 8 or less. Most commonly used in jewellery are agate ( a fine grained quartz), amber (the fossilized resin of the pine tree), and aquamarine is named for it's sea water color. Stones such as jade and jet; opal, pearl, and turquoise are also popular.
Agate when polished has variegated tones of blue, gray, green, brown and orange often divided by irregular milky coloured brands.
Amber a softish stone ranges from pale yellow and honey to brown, red brown and red and black. The absolute finest are clear, and the most prized contain embedded insects.
Aquamarine ranges from blue to green. Sky blue can be achieved by heating the stone.
Jade contains the mineral nephrite (hard and translucent and varies from white to shades of brown and green), and jadeite (rarer, harder and more brittle, can be dark green, green and lavender, emerald, or white and emerald but the translucent
emerald green is the most valuable.)
Jet is a type of coal (fossilized wood) that has a glossy black appearance. Associated with 19th-century mourning jewellery, rosaries, ornamental objects and cameos.
Opals are a form of silica, they are generally milky white, although tinges of blue, pink yellow or green may be present. Pearls are formed in the shells of mollusks such as oysters, mussels, and clams when foreign particles are enveloped by nacre, also known as mother of pearl. Pearls range in colour from shades of pink to black and are classified according to their shapes and luster. The most sought after pearls are drop shape known as spherical and have a satin sheen. Wild or true pearls occur naturally while cultured pearls are made by placing a foreign object in the shell. Turquoise is a blue-green gemstone. The bluer the stone, the greater its value.
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