On Serpentine. 29 



resemble tliose of the skin of a serpent (ojohis). It is, however, 

 probable that some of the early writers confounded under the 

 same name with the true serpentines the harder green porphyries, 

 which are very distinct. Linnaeus, who regarded serpentine as a 

 species of tale, described it under the name of talcum serpentinum^ 

 and the name of serpentine, synonymous with the Greek ojjJiifes, 

 and corresponding to the serpentirio of the Italians, is now univer- 

 sallj'' emploj^ed. 



Serpentine is a soft mineral, easily scratched with the point of 

 a knife, and gives a white powder somcAvhat unctuous to the touch, 

 a property which it has in common with talc and several other 

 minerals. Its colors are generally some shade of green, varying 

 from oil or leek green to olive or blackish green ; they are seldom 

 bright ; yellow and red serpentines are sometimes met with ; the 

 colour of the latter is due to mechanic allj^ intermixed red 

 oxyd of iron. The finer varieties are very often translucent, con- 

 stituting what is sometimes called nohle serpentine, but more 

 frequently the mineral is opaque, or only translucent in thin 

 fragments. Serpentine is generally massive and without any 

 visible structure ; it is tough and breaks with a conchoidal frac- 

 ture. Occasionally, however, it is met v/ith foliated or fibrous, 

 forming splintery masses like wood, the fibres being brittle and 

 elastic ; this variety has been named picroUte, The fibres some- 

 times become exceedingly fine, and are thin, soft a^id flexible, 

 with a silky lustre, constituting a variety of asbestus, difi"ering 

 chemically however from the true asbestus, which is a variety of 

 hornblende. This asbestiform serpentine has been called chry- 

 sotile. 



The lustre of the massive varieties of serpentine is feeble, and 

 somewhat waxy or resinous ; they are capable of receiving a fine 

 polish. Serpentine is comparative!}^ tender and easily wrought 

 when first taken from the quarry and yet moist, but becomes 

 hardened when exposed to the air. When moistened by breathing 

 upon or otherwise, serpentine gives a peculiar odour, like that of 

 clay ; hence called the argillaceous odour. The specific gravity 

 of serpentine is from 2.4 to 2.6, water being 1.0. 



As to its chemical composition, serpentine is essentially a silicate 

 of magnesia combined with water ; Avhen pure it should contain : 

 silica 43.60, magnesia 43.40, Avater 13.00=100.00 ; but a portion 

 of protoxyd of iron, amounting sometunes to 7 per cent., generally 

 replaces a part of the magnesia, and minute quantities of oxyd of 



