SILK 'ATI'S, TITANATKS, KT< 



443 



tion- <>f these two forms. ( Mlicr forms arc rare ; the mix- occurs on 

 Hystalfl from Mill Rock, New Haven, Conn., and the octahedron 

 on crystals from the isle of Elba. 



St nations appear on the dodecahedral face parallel to the long 

 diagonal, and on the trisoctahedral face parallel to its intersection 





jam. 



Flo. 483. Garnet Crystals in Schist. Southbury, Connecticut. 



with the rhombic dodecahedrons ; these striations appear on the 

 weathered or water-worn crystals also. 



The garnets form a very compact isomorphous group in which 

 there is a gradual transition from one variety to the other. They 

 are as a rule grouped under six heads, with varieties under each of 

 these. 



I. Grossularite, Calcium aluminium garnet, Ca 3 Al2(Si0 4 )3 ; 

 CaO = 37.30, A1 2 O 3 = 22.69, SiO 2 = 40.01 ; H. = 6.5; G. = 3.5; 

 Color, white, amber yellow to cinnamon brown, sometimes green 

 when chromium is present. Cinnamon stone, or hessonite, is a 

 brown variety, beautiful specimens of which are obtained from 

 Ala. Piedmont; also Ceylon; and Bethel and Rumford, Maine; 

 Amity, New York, and many other localities, as it is a common 

 variety of garnet. 



II. Pyrope; Magnesium aluminium garnet, Mg 3 Alo(Si0 4 ) 3 ', 

 MgO = 29.82, A1 2 O 3 = 25.40, SiO 2 = 44.78 ; H. = 7.5 ; G. = 

 3.7 ; Color, dark red to nearly black. 



This is the precious garnet of the jewelers, often called the 

 " Cape Ruby." Good pyropes are associated with serpentine at 



