ALUMINA. 



345 



The primitive rocks near New- York, and West-Farms in Westchester county, have been 

 given as localities of zeolite, but I have no means of ascertaining whether the specimens be- 

 long to this or to some other species which were formerly confounded under that name. 



It may be added, that fine specimens of mesotype occur, with various others of the zeolite 

 family, at Bergen hill, New-Jersey. 



STILBITE. 



[From the Greek rfnXSu, to shine, on account of its great lustre.] 



Stilbitc. Haay, Cleaveland, Phillips, Beudant and She^ard. — Prismatoidal Zeolite, or Stilbite. Jameson. — 



Frismatoidischer Kuphon-Spath. Mohs. 



Description. Colour white, sometimes grey, yellow or red. It occurs regularly crystal- 

 lized ; also in scopiform, stellular and foliated masses. Primary form a right rectangular prism. 

 Fig. 330. Fig. 330. Cleavage parallel to M and T, the former only perfect. Lustre 



vitreous ; the lateral faces of the prism pearly. Alternates from semi- 

 transparent to translucent. Hardness from 3 . 5 to 4 . 0. Specific gravity 

 from 2 . 00 to 2 . 20. Becomes opaque by heat. Before the blowpipe, 

 it exfoliates, and melts into a vesicular bead. Dissolves in acids ; with 

 difficulty forms a jelly in the cold. Its solution is precipitated by oxalate 

 of ammonia. 



Composition. Silica 52.50, alumina 17.07, lime 11.52, water 18.45 {Thomson). 



Geological Situation. Although usually found elsewhere in trap rocks, in the State of 

 New-York it occurs in veins and cavities in gneiss, white limestone and slate. 



LOCALITIES. 



New-York County. Small scopiform fibres or plates of a reddish or yellow colour occur 

 in thin veins coating gneiss and granite, at the Harlem tunnel. It is sometimes associated 

 with mesotype and epidote. 



Orange County. Stilbite is said to have been found at West-Point, in this county.* 

 Putnam County. Two or three localities of this mineral occur in Phillipstown. Crystals 

 Fig. 331. of the primary form (Fig. 330), and the modification represented in Fig. 



331, have been found near Coldspring. M. on d 133° 30'. The crystals 

 are often grouped resembling a fan, and have a wax-yellow colour. 

 Opposite West-Point, where a locality of this mineral was discovered 

 Mi'' by G. Kemble, Esq., it occurs in a decomposing cellular bluish feldspar, 



forming a vein in gneiss. The crystals are of a honey-yellow colour, of 

 the primary form, with several smaller and gradually diminishing cunei- 

 form crystals applied to t^o opposite sides ; giving them a radiated ap- 



MiN. — Part II. 



* Torrey. American Journal of Science. IX. 402. 



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