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A type of quartz. Its name originates from the Sanskrit word "upala" meaning precious stone. They are luminous and iridescent with inclusions of many colours. Opals show a shifting of spectral colours. They are found in Mexico, Brazil, the USA, Japan, Honduras, Kenya, Czechoslovakia, Peru, Canada. ...
Onyx refers to a black and white banded variety of agate. Brown varieties are named sardonyx. It is composed of relatively straight, parallel layers of different colours. It is usually cut into cabochon (convex hemispherical or oval form, polished but not cut into facets) or into beads, and is ...
Opaque to translucent precious gemstone composed mainly of lazurite and calcite. Its name originates from the Persian word "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 ...
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, made superior weapons and tools for early man. It was not until the 19th century that a ...
Garnets are nesosilicates. Its name originates from ancient Greek as the colour resembled pomegranate seed or granatum. Garnets do not show the tendency of crystalline materials to split along definite planes, creating smooth surfaces, called cleavage, therefore, when they fracture under stress, ...
Emerald is a valuable Beryl that owes its colour to chromium or vanadium, which make it bright green. Emeralds can have many flaws and, therefore, 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 ...
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 ...
The hard skeleton of red coral branches, made up mostly of calcium carbonate, which is durable and intensely coloured. Coral can be polished to a glassy shine. Usually deep water corals have light colour, while shallow water corals have deep colour. Coral jewellery has been found in ancient ...
