CRYSTALLOGRAPHY OF THE EPIDOTE. 



300 



are OP j 001 [ , «. P s j 100 J , 2 P oo I 201 J , oo P So j 010 J , and 

 occasional]}' two small hemipyramids, probably + P Til and — P 



111 . The crystals, as well as many of the intergrowths with allanite, 

 occur as a rule completely surrounded by biotite. 



,?<• 



Figure I.— Microscopic Crystal of Epidote in 

 Ellicott City (Maryland Granite. 



Fi<.i be 2. — Epidote in Ellicott City 

 Granite. 



An interesting occurrence of epidote is as an inclusion in sphene, 

 along with an apatite and a greenish mineral having all the optical and 

 physical characters of pleonaste. In other masses the sharply bounded 



Figube 3.— Epidote in Woodstock 

 (Maryland) Granite. 



Figube 4.— Epidote in Wood ' < 

 Granite. 



epidote comes in contact with unaltered feldspar, quartz and biotite 

 grains and gives outlines to them. 



Its Origin. — The origin of the epidote in the granite rocks under con- 

 sideration is of great interest. Rock-making epidote has been regarded 



