veneers of it are employed with very bad effect in the decoration of vases, furniture, and even doors. Its hardness is 4, and its specific gravity 4.
The concentric veinings and markings of malachite, showing its deposition from water, vary in depth of tint and often exhibit a satiny texture.
Malachite belongs to the hydrated carbonates, and is reprerepresented by the chemical formula Cu Co₃, Cu H₂O₂; it is therefore near chessylite or azurite 2 Cu Co₃, Cu H₂O₂, Malachite contains, in percentages, about the following proportions of its three constituents:
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Copper oxide 72
Carbon dioxide 20
Water 8
Lumachella
Is a precious marble. It consists of a brown limestone, in which occur numerous fossil shells, having brilliant fiery red, green, or yellow chatoyant reflections. It comes from Bleiberg in Carinthia, and from Astrakhan. It is an impure carbonate of lime.
Pearl.
Although nearly all those bivalves which have nacreous shells do occasionally produce pearls, there are two mollusks which must be regarded as pearl-bearers par excellence. These are the pearl oyster and the pearl mussel.
The best-known pearl oyster is the small species, Margaritifera vulgaris, which yields the famous pearls of Ceylon. A larger species, Meleagrina margaritifera, occurs in the Persian Gulf, Madagascar, the west coast of Central America, California, and West Australia. The shells of these oysters are particularly valued on account of the mother-of-pearl which they yield. From the pearl-mussel, Margaritana margarilifera, which belongs to the Family of the Unionidæ, the pearls of Scotland, North Wales and the English District are derived. These British pearls possess, generally
