484 MINERALOGY 



gregates, often restricted in the middle or sheaf-like, a form very 

 characteristic of stilbite. Twinning also as in harmotome. When 

 the crystals are tabular and simple, the very strong pearly luster on 

 the orthopinacoid has the appearance of fish scales. 



Chemically the calcium may be replaced in part by sodium, and 

 the brown color of some specimens is due to the presence of iron. 

 Stilbite is a common mineral in the cracks of the basic eruptive 



FIG. 503. Stilbite from Nova Scotia. 



rocks. Very fine white specimens have been taken from the rail- 

 road cuts through Bergen Hill, New Jersey. It is also found in the 

 trap quarries at Moore's Station, New Jersey, where it is associated 

 with natrolite, prehnite, calcite, and pectolite. 



Cabinet specimens are obtained at Partridge Island, Nova Sco- 

 tia and the Lake Superior region. 



CHABAZITE 



Chabazite. (Ca . Na 2 ) Al 2 (SiO 3 ) 4 . 6 H 2 ; Hexagonal ; Type, Di- 

 hexagonal Alternating ; 6 = 1.0860; 000 1_ A 1011 =51 26'; 1011, 

 1011=85 14'; Common forms, r (lOfl), e(0112), s (0221) ; 

 Twinning axis 6, interpenetration twins ; Cleavage, rhombohedral 

 distinct; Brittle; Fracture, uneven; H. = 4.5; G. = 2.08-2.16; 

 Color, white, yellow, gray, flesh-red, or pink; Streak, white; 



