VOL. XII, 



PROCEEDINGS OF THE NATIONAL MUSEUM. 599 



Smitbfield, Rhode Island, which it at times resembles. Under the micro- 

 scope the serpentine shows a platy, almost fibrous structure, the plates 

 in each case lying approximately parallel with tbe vertical axes of the 

 crystals from which they were derived. These plates do not extinguish 

 simultaneously, but the alternate bands become in a general way light 

 and dark as the stage is revolved between crossed nicols. The dark 

 cloud, however, sweeps over in so indefinite a manner that nothing like 

 extinction angles are obtainable. An analysis of the serpentine matter 

 (70350) by Mr. Catlett yielded results as below : 



Si0 2 39.92 



A1 2 3 08 



Fe 2 3 50 



MgO 42.52 



CO, 1.64 



CaO 90 



Moisture (at 105°) 1.36 



Ignition 13.26 



100. 18 



For the material examined from this locality the Museum is indebted 

 to Mr. George F. Kunz. 



C— OLD WOLF QUARRY, CHESTNUT HILL, NEAR EASTON, PENNSYLVANIA. 



This serpentine, as is well known to American collectors, is of a 

 light oil green or yellowish color, closely resembling that of Montville, 

 New Jersey. As noted in the reports of the Pennsylvania Survey*, 

 it occurs associated with calcite, gray limestone, asbestus and tremo- 

 lite. The pure varieties, such as find their way into the cabinets of 

 collectors (70125), are not obtainable in masses of any size, but occur 

 in seams or sporadically scattered throughout a massive tremolite rock 

 which is here quarried, and, after pulverization, used as a filler in paper 

 manufacture. A beautiful bright yellowish green vermiculite (?) also 

 occurs here. This will be described in another paper. 



The association of the serpentine with the white tremolite rock is 

 such as to suggest a genetic relationship. Indeed, it is possible in the 

 quarry opening to trace the gradual passage, often within the distance 

 of a few inches, of the pure white tremolite rock into a mixed rock com- 

 posed mainly of serpentine, tremolite, and calcite (specimens 70114, 

 70115, 70119, 70122, 70123). Thin sections of the fresh tremolite 

 (70122) rock show a compact aggregate of white non-pleochroic, some- 

 what fibrous crystals, with tbe cleavage of hornbleude and giving ex- 

 tinctions on clinopinacoidal sections running as high as 20°. As ser- 

 pentinization has set in the tremolite crystals are broken up into fibrous 

 aggregates traversed by irregular canals of the serpentinous matter, the 

 direction of which has been but little controlled by the cleavage lines 



* Rep. D 3 , Second Geol. Survey of Pa., p. 79. 



