346 



DESCRIPTIVE MINERALOGY. 



Ml 



pearance, witli deep reentering angles on the sides. The summits are truncated at the termi- 

 nal edges, and slightly bevelled in the direction of the laminje of the crystal, which is also 

 the case with the cuneiform additions.* 



Fig. 332. 



Rockland County. It is found in minute crystals in veins, with other zeolitic 

 minerals, in the greenstone at Piermont. Fig. 332 represents a form observed 

 here and at Bergen hill, New-Jersey. The specimens from the latter locality far 

 exceed in beauty those heretofore found at Piermont. The crystals are nearly 

 transparent, and although small, present very highly finished and brilliant faces. 

 At Bergen hill, this mineral is also found in grouped or fasciculated crystals of a 

 straw-yellow colour. 



Westchester County. Near West-Farms, stilbite occurs in crystals lining the walls of 

 seams in gneiss, with chabasite, heulandite and epidote. The colour varies from pale to deep 

 red. It is also found near Bronx creek, in white six-sided tables, in an aggregate of epidote, 

 hornblende, quartz and carbonate of lime, and in gneiss near Yonkers. 



This mineral has recently been obtained in scopiform crystals of a dull 

 yellow colour, sometimes with perfect terminations, near Peekskill. The 

 vein is apparently from one half to three quarters of an inch wide, and is 

 in a decomposing slate. The form represented in Fig. 333, has been found 

 at this locality. 



In Connecticut, stilbite is met with in seams in gneiss at Hadlymc, 

 associated with heulandite, chabasite, etc. It is also found at Saybrook in 

 the same State, and at Bellows-Falls in Vermont. 



Fig. 333. 



M 



HEULANDITE. 



[In honour of Mr. Heuland, of London.] 



Stilbite. Ilauij and Ckaichind. — Foliated Zeolite, ^ycrner. — Hemi-prismatic Zeolite, or Heulandite. Jameson. — 

 Hemiprismatischer Kuphon-Spath, Mohs. — Heulandite. Bcudant, Phillips, Shcpard and Dana. 



^'"••'^*' Description. Colour white, grey, red and brown. It occurs re- 



gularly crystallized ; also massive, and often globular. Primary form 

 a right oblique angled prism. Fig. 334. M on T 130°. Cleavage 

 parallel with P, highly perfect. Fracture conchoidal. Lustre vitreous, 

 except P, which is in a high degree pearly, both as faces of cleavage 

 From transparent to translucent on the edges. Hardness from 3.5 to 

 4.0. Specific gravity from 2.20 to 2.50. Before the blowpipe, it melts with intumescence, 

 emitting at the same time a phosphorescent light. It does not gelatinize with acids. 



and of crystallization. 



* Torrey. American Juurnal of Science. V. 399. 



