Serpentine,

Serpentine, a mineral composed of silica and magnesia in almost equal proportions, with about 13-15 per cent. of water, and a little protoxide of iron. Serpentine occurs generally massive; never in crystals, save as pseudomorphs; colour some shade of green, also red and brownish yellow; has a smooth but sometimes greasy feel; is soft enough to be scratched with calcite. Precious Serpentine, or Noble Serpentine, is of a rich, dark-green colour, hard enough to receive a good polish, translucent, and sometimes contains imbedded garnets, which form red spots, and add much to its beauty. It is a rare mineral. It occurs at Baireuth in Germany, in Corsica, at Portsoy in Banffshire, in the Shetland Islands, &c. It is generally found along with foliated limestone associated with schistose rocks. The ancient Romans used it for pillars and for many ornamental purposes; and vases, boxes, &c. are still made of it, and much prized. The ancients ascribed to it imaginary medicinal virtues. Marmolite is a scaly, foliated serpentine; Chrysotile is a delicately fibrous variety, with a silky lustre, often met with as veins in ordinary serpentine. Common Serpentine is a rock rather than a mineral. It often occurs in winding irregular veins; hence the name serpentine. It is generally green or red, the colour being sometimes uniform, at other times mottled, spotted, streaked, veined, or clouded. It occurs not only in veins, but forming irregular sheets and masses, and is usually associated with crystalline schists and granitoid eruptive rocks. The mineral serpentine is always a product of the chemical alteration of other minerals; and there is reason to believe that most of the masses of serpentine are highly altered igneous rocks which were rich in olivine or peridote. Many peridotites are proved to have been altered into serpentine. Concerning the origin of some of the serpentes associated with the crystalline schists there is still much uncertainty.