552 ANALYSIS OF SERPENTINE. 



" Several European specimens, from unknown localities, were found to consist of asso- 

 ciated magnesian minerals, cemented by anhydrous carbonate of magnesia. As a general 

 expression, asbestus is the most abundant simple mineral, and it presents itself under 

 forms in which it is recognized with difficulty. Talc is also largely intermixed in the 

 basis rock. The coloring material of serpentine is found in several minerals, and al- 

 though here included as a silicate of the proto-peroxyd of iron, I have deemed it worthy 

 of a particular examination, at a future time." 



In respect to the last point, we would inquire whether the constituent water may not 

 give the color. For if the green color was derived from a salt of iron, then when the rock 

 was heated to a redness the green color would change to red, the color a higher oxyd of 

 iron ; just as the Vermont yellow ochres and clays, when heated, change to red ochre and 

 bricks. But if the constituent water gave the green color, then would the serpentine 

 become white when heated. This inquiry was suggested to us in Warren, where a large 

 pile of white calcined serpentine was shown to us, which had formerly been burnt for 

 lime by persons who were unacquainted with its composition. It had been exposed 

 to the weather for many years, yet the red color of the peroxyd of iron was nowhere 

 apparent. 



The researches relating to the composition of these serpentines have an important 

 bearing upon our theories respecting the origin of these rocks. Dr. Hayes' views go to 

 show that the serpentine rocks are of aqueous or hot water origin, as a heat above that of 

 500 F. is inconsistent with their chemical composition. 



Geological Position, Equivalency, Origin and Metamorphism of Steatite. * 

 Steatite is undoubtedly a variety of talc, both of whose normal composition is 



Silica, 62.61 



Magnesia, 32.51 



Water, 4.88 



100.00 



In Vermont, indeed, the purest varieties of steatite, or soapstone (which here is the 

 more usual name), are talc, whose folia adhere together firmly enough to be formed into 

 blocks. In common soapstone the folia seem to be crowded together, and frequently 

 mixed with some other minerals. 



Talc is a distinct hydrous silicate of magnesia. Chlorite contains only half as much 

 silica, and takes alumina and iron into its composition as essential ingredients. Never- 

 theless we have not attempted to distinguish between the light colored steatites of 

 Vermont, and those green and more compact varieties, which form the most valuable of 

 soapstones, but which we have supposed to be chlorite ; though in the absence of analysis 

 it would not be strange if they should turn out to be green talc. 



The steatite of Vermont generally forms limited beds in talcose schist. It occurs, also, in 

 mica schist, as at Cavendish, in gneiss at Grafton, and near Perkinsville in Weathersfield. 



Hornblende schist also sometimes forms at least one of the walls, and on the Hoosac 

 range of mountains in Massachusetts, which is a continuation of the Green Mountains, 



*By E. Hitchcock, Senior. 



