472 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 58. 



not seen in contact with the topaz, although occurring in the same 

 hand specimen with it. The sphalerite is easily confounded with 

 wolframite, which it greatly resembles. Its streak is dark brovai, 

 and when the powder is examined under the microscope it is seen to 

 be very dark brown in color, transparent, and wholly isotropic. 



GARNET. 



Brownish red granular garnet occurs both in the main pit and 

 in the limekiln opening in nodular or lenticular masses in marble 

 which may reach a foot in greatest diameter. Where such masses 

 have had the surrounding calcite dissolved away small dodecahedral 

 crystals are revealed. 



PYROXENE. 



The green granular pyroxene, cocoolite, occurs in the main pit and 

 especially in the limekiln pit in grayish green grains distributed in 

 lines parallel to the bedding. It is to this mineral that the marble 

 ewes much of its banded appearance. White malacolite occurs 

 sparingly in the marble. These minerals are of the types common 

 throughout the Berkshires and warrant no special description. 



PHLOGOPITE. 



Phlogopite occurs sparingly as small copper-red scales in the 

 marble of the limekiln opening. 



TOURMALINE. 



Some large blocks on the dump of the main pit are composed of 

 fine acicular black tourmaline embedded in vitreous grayish quartz. 



HORNBLENDE. 



A common green hornblende occurs with coccolite and under the 

 same conditions in the limestone. 



FLUORITE. 



Fluorite, varying abruptly from rose pink to deep purple in color, 

 occurs at the upper mine opening intimately intergrown with fibrous 

 scapolite. At the Limekiln Vein fluroite of a purple color occurs in 

 granular masses of considerable size. Veinlets of coarse foliated 

 margarodite, made up of interlocking crystals, have the crystals 

 separated by thin layers of fluorite, and deep purple fluorite forms 

 thin plates between the plates of mica. Eather broad cleavable 

 masses of colorless to pale salmon or brown fluorite occur associated 

 with fibrous margarite. In the breaking down of the abundant topaz 

 to form muscovite the liberated fluorine has recombined with the 

 available lime to form fluorite. 



