Serpentine. 



365 



12. SERPENTINE. 



Perhaps there is no rock about whose true nature and geological 

 relations so little is known as serpentine. Its external characters are 

 not, indeed, obscure ; and analysts have given, probably with accu- 

 racy, its ultimate elements. But is it an altered or unaltered rock ? 

 If altered, what was the original rock % Is it stratified, or unstrati- 

 fied % primitive, or transition 1 These are questions on which geolo- 

 gists are not yet agreed. The Dictionnarie Classique D'Historie 

 Naturelle, says, that serpentine is " principally situated in the latest 

 of the primitive rocks and in the intermediate class." Brongniart 

 doubts whether it is found so low as the primary rocks ; {terrains 

 agalysiens ;) and he says that " no rock of this group, ( Ter. Plut. 

 Ophiolithique,) exhibits even a tendency to stratification."* De La 

 Beche classes it with the unstratified rocks. f But Dr. Maculloch 

 considers it as sometimes stratified and sometimes unstratified ; and 

 accordingly ennumerates it in both these classes ;J and also as a 

 venous rock. He says, also, that it occurs in connection with gran- 

 ite, gneiss, micaceous, chlorite, and argillaceous schists. His ac- 

 count of this rock corresponds most nearly with its characters in 

 Massachusetts ; and here, if I mistake not, it is almost always strati- 

 fied. At least, the exceptions are less important than in the case of 

 limestone ; and since I have placed all our limestones in the stratified 

 class, I shall do the same with our serpentines. In almost all cases, 

 also, our serpentines are connected with the oldest rocks ; such as 

 gneiss, mica slate, and talcose slate : and if we have any rocks that 

 are primitive, serpentine is one of the number. 



Mineralogical Characters. 



1. Compact Serpentine. This embraces two mineralogical varie- 

 ties, the common opaque serpentine, and the translucent delicate 

 green noble serpentine. They are of various degrees of hardness, 

 and their fracture is sometimes splintery, sometimes granular, and 

 sometimes foliated-splintery. The colors and their intermixture are 

 very various. (Nos. 870 to 885.) 



2. Serpentine and Talc. The talc is either foliated or in the con- 



* Tableau des Terrains, &c. p. 350. 



t Geological Manual, Second Edition, p. 487. 



t System of Geology, Vol. 2. p. 197. 



