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LXV. Theſe are of peculiar Excellence and Value. And there are yet alſo ſome others to be mentioned; as the foſſile[1] Ivory, which is variegated with
- ↑ Foſſile Ivory and Bones of Animals lodged long before in the Earth, are frequently dug up in all Parts of the World. Theſe Subſtances have preſerved their Texture, Solidity, and Colour, in different Degrees, according to the Nature of the Matter among which they have lain: Sometimes they are dug up firm, ſolid, and ſcarce altered; ſometimes ſo rotten, as to crumble to pieces in handling; and ſometimes ſtained to various Colours, from the diſſolved Particles of metalline or mineral Matter among which they have been lodged.
Of this Kind is the Turquoiſe, generally eſteemed and called a Stone, but, in reality, no other than the Bones and Teeth of Animals, accidentally lodged near Copper Mines, or Places where there is cupreous Matter in the Earth. This Metal, if diſſolved by a proper acid Menſtruum, makes the Bone a green Turquoiſe, of which there are ſome found in Germany and elſewhere: And if the cupreous Particles have been diſſolved in a proper alcaline Menſtruum, they convert the Bones or Teeth, into the Subſtance of which they penetrate, into the com-
cence from the Animal in which it is found: it conſiſts of ſeveral Laminæ laid cloſely round one another, as the Bezoar, the Calculi in human Bladders, and other animal Stones. When ſmall, ſuch are called Seed-pearls, and when larger than ordinary, Uniones. Our Jewellers diſtinguiſh them into Oriental and Occidental. They are found in many Places, as well as in different Shells. The fineſt in the World are thoſe of the Perſian Gulph: There are a great number found about Cape Comorin and the Iſland of Ceylon, but they are greatly inferior to the Perſian. Very large ones have been found about Borneo, Sumatra, and the neighbouring Iſlands, but not of the fine Shape and Water of the Perſian.
The Occidental have a milky Caſt, and want the poliſhed Gloſs of the Oriental. They are very plentiful in many Parts of America; as alſo in France, Italy, and Scotland; and we meet with them every Day in our Oyſters and Muſcles here, but ſeldom of any great Beauty.
Some have been of Opinion, that they were bred ſingly, one only in a Shell; and that they thence had their Name Uniones; but this, is an Error, many being very frequently found together; nay, there are Accounts of one Shell producing 120.
