616 MINERALOGY 



Andalusite ; Orthorhombic ; n = 1.64; \ a = .011. 



Prismatic or square crystalline outlines, or grains; 

 Cleavage prismatic, at times well developed; Color- 

 less, reddish, or spotted ; Relief marked ; Pleochroism 

 strong in colored specimens ; Interference colors first 

 order grays to yellow ; Extinction parallel ; Axial 

 angle large; Optically negative ( ) ; p. 459. 



Hypersthene; Orthorhombic; n = 1.67; "y a = 

 .013. 



Prismatic, fibrous or in grains ; Cleavage prismatic, 92, 

 also parting (010); Color, shades of brown; Relief 

 marked ; Inclusions of plates or rods parallel arranged, 

 characteristic ; Pleochroism increases with the depth 

 of color; Interference colors gray, yellow, to orange 

 of the first order; Optically negative ( ); p. 421. 



Staurolite; Orthorhombic; n = 1.741 ; -y a = .010. 

 Short prismatic crystalline outlines ; Twins common ; 

 Color, shades of yellow or brown ; Cleavage prismatic 

 and 010 distinct ; Relief marked ; Pleochroism chang- 

 ing from reddish to yellow; Large crystals contain 

 many inclusions; Interference colors first order yel- 

 low to orange ; Parallel extinction ; Axial angle large 

 Optically positive (+) ; p. 477. 



Epidote ; Monoclinic ; n = 1.751 ; \ - a = .032. 



Crystals elongated parallel to the orthoaxis, or granular ; 

 Cleavage basal, well developed ; Color, shades of green,, 

 brown to colorless ; Relief well marked ; Extinction 

 parallel in elongated sections, otherwise the angle is 

 small ; Pleochroism increases with the depth of color 

 of the specimen ; Interference colors third order ; 

 Optically negative ( ) ; p. 466. 



Titanite; Monoclinic; n = 1.938; -y a = .145. 



In wedge-shaped crystalline outlines or granular; 

 Cleavage prismatic, distinct, seldom parallel to the 



crystalline outline ; Brown, yellow to colorless ; 

 Relief very marked ; Interference from low orders to 

 very high ; Extinction angles not characteristic ; 

 Pleochroism increases with the depth of color of the 

 specimen; Optically positive (+); p. 503. 



