The Monoclinic Pyroxenes of New York State. 173 



The pyroxene is therefore, as pointed out by Dr. Merrill, a very 

 pure lime magnesian variety, corresponding pretty nearly to the 

 formula of diopside CaMgSigOg, and its conversion into serpen- 

 tine consists in the assumption of water and the giving up of its 

 lime, which crystallizes as calcite. A comparison of the preced- 

 ing analysis with that of the white pyroxene analyzed by the 

 writer, and given on a previous page, shows a close similarity in 

 composition. The latter corresponds still more closely, however, 

 with the white pyroxene which Dr. Merrill has described from 

 Montville, N. J. The composition of the latter is : 



SiOa 51.45 48.17 



Ignit 1.08 .12* 



CaO 24.02 21.96 



CaCOs 10.44 



MgO 18.43 17.61 



MgCOa .71 



AlA"- 2.94 .52 



FeA 1.06 .18 



FeO 96 .24 



MnO tr 



SO3 tr tr 



K2O und. und. 



NajO und. und. 



99.94 99.95 



In this connection there may be mentioned the serpentine 

 which was found in aqueduct shaft 2 (Ref. 33) in New York city. 

 It results from the hydration of a white monoclinic pyroxene, 

 showing under the microscope nearly rectangular prismatic 

 cleavages, and giving extinction angles as high as 44°. The 

 alteration is accompanied with the formation of abundant secon- 

 dary calcite. 



Beck (Ref. 2, p. 289) has noted a light green pyroxene from a: 

 locality half a mile north of Port Henry. It is said to be inti- 

 mately mixed with secondar^^ calcite. 



Bussel, St. Lawrence Go. — In addition to the greenish-black 

 crystals from this locality which were mentioned under the head 

 of augite, there are found greenish-white crystals resembling the 

 forms from DeKalb and also green glassy ones of prismatic habit. 



The greenish-white ones are nearly always stronglj^ tabular 

 parallel to 6(010), and were observed to have the following com- 



* H,0. 



