554 ORIGIN OF SERPENTINE. 



of magnesia, and 12.87 of water. Most serpentines contain alumina and iron in consid- 

 erable quantity, and often some lime, potash and soda ; but these seem not to be essential. 



According to these views, serpentine may have been derived from the same minerals as 

 steatite : such as hornblende, mica, feldspar, garnet, augite, &c. Indeed it seems probable 

 that some beds of hornblende schist and diorite, or greenstone, have been changed into 

 serpentine. Hornblende, but rarely greenstone, is often associated with it in the Green 

 Mountains, and such a metamorphism is quite possible. Sir William Logan, however, 

 is of opinion that the Green Mountain serpentines have resulted from changes in silicious 

 dolomites and magnesites. But since it might be derived from so many sources, it is not 

 probable that sometimes it may have resulted from the metamorphosis of one mineral 

 and sometimes another ? We think that by a careful examination of the numerous beds 

 of serpentine in Vermont, the remnants of the different formations from which it was 

 derived, such as dolomite, hornblende rock, talc, steatite, chlorite, &c., may be discovered. 

 The connection between serpentine and steatite is seen almost everywhere, and the two 

 rocks often pass insensibly into each other, so that specimens of almost every intermediate 

 grade may be found. A good locality for seeing this is near the Rutland and Burlington 

 Railroad, a little west of Proctorsville. Here enormous masses of serpentine are inter- 

 posed between strata of mica schist and steatite. Between the latter rock and serpentine 

 there is generally no well marked division, and if anywhere in the State we could find 

 evidence that the two rocks had been forced together, it would be here. Yet neither of 

 them appear to have been protruded into the strata of schist ; but the most satisfactory 

 explanation of the phenomena is, that both of them are products of metamorphism in the 

 wet way, as already described. Why the whole mass was not pushed to the ultimate 

 limit of metamorphism, which we suppose to be serpentine, rather than steatite, we con- 

 fess ourselves unable to show ; though we presume it depended upon the temperature, or 

 the character and amount of ingredients held in solution by the water of metamorphism. 

 We think that these points will ere long be settled by the researches of chemical geology. 

 But it will require careful and laborious investigations. 



If the views above expressed are correct, the age of the serpentine is probably the 

 same as that of the steatite and the talcose schist. On this point we have already stated 

 all that we know, which indeed is but very little. 



As to the stratification of serpentine, our conviction is, that ninety-nine-hundredths of 

 the rock in Vermont do not show it any more than granite. Indeed, we think that all 

 the divisional planes in it are superinduced. Where it passes into talc, or steatite, it 

 exhibits a somewhat foliated structure, whose strike and dip correspond to those of the 

 adjoining schists, and may therefore correspond to the original stratification before the 

 metamorphism of the rocks. We think, however, that it does not show any more distinct 

 marks of stratification or of foliation than we have seen in syenite. 



The distinction between stratified and unstratified rocks has been usually regarded as 

 one of the most trenchant and reliable in the science of geology. And so long as it was 

 considered a certain fact, that the stratified rocks were exclusively deposited by water, and 

 the unstratified all melted by dry heat, it is not strange that geologists should have 

 looked upon the line between the two classes as very distinct and recognizable. But now 

 that it is so generally admitted that hot water has been the most efficient agent in 



