428 



MINERALOGY 



clinic ; Type, Digonal Equatorial ; a : b 

 P = 84 40' = 001 A 100; 100 A 110 = 47 

 10'; 001 A Oil = 44 29'; Forms, c (001), a 

 w (140) ; Twinning plane, 100 ; Cleavage, a 

 Fracture, uneven ; H. = 5 ; G. = 2.68-2.8! 

 Streak, white ; Luster, silky ; Transparent 

 y a = .038 ; Axial plane perpendicular to 

 of 90 nearly with the axis c ; Bx a = b ; 2V - 



:c= 1.1140: 1:.9864; 



57' ; 001 A 101 = 39 

 (100), h (540), q (340), 

 and c perfect ; Brittle; 

 I ; Color, white, gray ; 

 to opaque; n = 1.61 ; 



010, making an angle 

 = 60; Optically (+). 



B.B. Fuses quietly, coloring the flame yellow (Na). Gelat- 

 inizes with HC1; the solution freed of silicia yields little or no 

 precipitate with ammonia, but a heavy white precipitate with 

 ammonium carbonate (calcium). 



General description. Crystals are elongated and needle-like, 

 in radiated, nodular masses, with an opaque porcelain appearance 

 or silky ; sometimes in groups of long, slender and parallel, though 



FIG. 475. Pectolite. Franklin, New Jersey. 



individual, crystals. Elongation is parallel to the orthoaxis, with 

 the base and orthopinacoid as the prominent faces, terminated by 

 h and w. Tabular crystals are rare, but they have been found at 

 Bergen Hill, New Jersey. 



Pectolite is found as a secondary mineral in the cracks and cavities 

 of the basic eruptive rocks, where it has been deposited by percolat- 

 ing waters and associated with zeolites, calcite, apophyllite, and 

 datolite. It is a common mineral in the traps of Bergen Hill and Pat- 

 erson, New Jersey ; Isle Royal, Michigan ; Magnet Cove, Arkan- 



