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.
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 repre-represented by the chemical formula ; it is there-
fore near chessylite or azurite 2 Malachite con-
tains, in percentages, about the following proportions of its three constituents :
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.
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 margaritifera, which belongs
to the Family of the Unionidse, thepearls of Scotland, North Wales and
the English Lake District are derived, These British pearls possess,