476 I'ROCEKDlNCti OF THE NATIONAL MUSEUM. vol. oS. 



very small; optically positive; acute bisectrix perpendicular to the 

 perfect cleavage. Scales wholly irregular. 



Refractive indices : 



a=1.606±.003. 



/3=1.606±.003. 



7=1.610±.003. 

 a-7= .008±.0O3. 

 Pleochroism distinct : 



a=(k'ep blue green. 



j9=(ieep blue green. 



7=«=pale brownish green. 



These two chlorites, while essentially identical in all properties 

 except refractive index, dilfer sharply in this respect. It is regret- 

 able that additional analyzed prochlorites were not available for 

 comj^arison. Until the properties, both chemical and optical, of this 

 group are more fully known, the Trumbull material must be included 

 with prochlorite, despite the difference in refractive indices. 



EPIDOTE. 



A block of material in the dump of the upper mine consisted in 

 large part of a columnar ash gray to brownish gray or nearly white 

 mineral in prismatic crystals imbedded in glassy quartz. There is 

 a small amount of green hornblende in the quartz and patches of 

 calcite occur as the last deposit in cavities.^ By dissolving out Ihe 

 calcite, clear brown to gra}^ crystals of the prismatic mineral are 

 obtained. These resemble zoisite, but when measured were found to 

 have the angles of epidote. The prisms are formed by elongation of 

 the dome zone parallel to the b axis, which is the characteristic habit 

 of epidote. Terminations are rare, and when they occur they are 

 very simple with imperfect faces. Upon analysis the following 

 results were obtained : 



Analysis of epidote from TniwhnU. 



Per cent. 



SiO^ 36. 89 



AI2O3 28. 50 



Fe203 5. 92 



FeO . 52 



CaO 27. 26 



MgO . 21 



MnO . 02 



H2O 1. 29 



F . 60 



Total 101.21 



1 Specimens entirely similar to this preserved in the United States National Museum 

 contain a nearly white scheelite in grains and masses and are labeled " ore, Trumbull, 

 Conn." (Cat. 73696.) 



