GUIDE TO THE MIXERALOG10 COLLECTIONS 



105 



in the direction of the orthoaxis producing forms of horizontal 



prismatic habit (fig. 227). These pass into acicular tonus, stri- 

 ated in the direction of elongation, columnar, parallel or diver- 

 gent, and fibrous masses (pi. 31J. It also 

 occurs coarse to fine granular. The luster is 

 vitreous, the crystals sharp and with bril- 

 liantly reflecting faces; the color is com- 

 monly some shade of pistachio-green, often 

 nearly black, also yellowish green, gray or 

 brown. 



Epidote occurs in metamorphic rocks of the older formations, 

 in gneiss, mica and hornblende schists. It is found associated 

 with quartz, the feldspars, actinolite and minerals of the chlorite 

 group. It is common in Xew England and in many of the west 

 ern states. Handsome specimens have been found in Orange 

 and Putnam counties, X. Y. 



Axinite H,Ca i (B0)Al,(Si0 4 ) r ,( ?) 



Axinite is an aluminium and calcium borosilicate with some 

 of the calcium replaced by iron and manganese. It occurs in 

 sharp triclinic crystals with acute edges (fig. 228), 

 clove-brown, bluish or yellow in color and in 

 lamellar and curved lamellar masses. The luster 

 is highly vitreous. 



Prehnite H,Ca,Al,(SiQ.,).. 

 Prehnite is an acid calcium and aluminium 

 mi hosilicate. 



It is rarely found in isolated ort horhoiubic crystals of tabular 

 habit but usually occurs in aggregates of such crystals united 

 by their basal planes and producing barrellike, sheaflike and 

 botryoidal shapes (pi. 31,) with crystalline surfaces. The luster 

 is vitreOUS, faint pearly on the basal planes; the color is light 

 green to oil green, yellowish green, graj i<> while. 



Prehnite occurs as a secondary mineral in veins and cavities 

 in basic eruptive rocks, basalt, diabase, etc. also in gneiss anil 

 granite associated with calcite, pectolite, datolite and the /.eo 



lites. It is sometimes associated with the copper of the Lake 

 Superior region. Beautiful specimens are found in the neigh- 

 borhood of Bergen TT ill and Paterson X. -I. 

 It is occasionally cul us a gem. 



