248 DESCRIPTIVE MINERALOGY. 



for by tlie delicacy of the crystalline groups employed. In other respects, the opinion that 

 the variety described above, and the acicular globules of pharmacolite, belong to the same 

 species, is grounded solely on the analogy of resemblance existing between the former with 

 crystals of gypsum, and between the latter and the radiated groups so frequently observed in 

 the same species." According to Dr. Turner, the crystalhzcd mineral described by Haidinger 

 is composed of arsenite of lime 79.01, water 20.99.* 



LOCALITIES. 



A mineral apparently belonging to this species, has been found by Dr. Horton in magnetic 

 iron ore, in the town of Momoe, Orange county. 



ORDER IV. MAGNESIA. 



This order embraces the following minerals, viz : 



1. Brucite (Hydrate of Magnesia.) 3. Epsom Salt. 



2. Carbonate of Magnesia. 4. Magnesian Carbonate of Lime. 



5. Hydrobromate of Magnesia. 



BRUCITE. 



[In honor of the late Dr. Archibald Bruce, of New- York.] 



Brucite. BevAant. — Hydrate of Magnesia. Ckaveland, Phillips, Thomson and Shepard. — Native Magnesia. 

 Bruce. — Prismatic Talc-Mica, var. Jameson. 



Description. Colour white, inclining to green, and also grey. Streak white. It occurs 

 in plates which have a lamellar structure, and sometimes in prismatic concretions that point 

 to the regular six-sided prism. It is easily split into thin flexible lamina. Lustre shining, 

 and somewhat pearly. Semi-transparent in the mass, and transparent in single foha. Hard- 

 ness 1.0 to 1.5. Gives on paper a polished pearly trace. Specific gravity 2.35. Before 

 the blowpipe, it gives out water, but is not fusible. By the oxyhydrogen blowpipe, however, 

 small portions of it may be fused into an enamel. It is soluble without effervescence, in 

 dilute muriatic, nitric, and sulphuric acids. 



* Brewster's Edinlmrgh Journal of Science. III. 303. This volume also contains the paper of Mr. Haidinger, from which the above 

 extract is made. 



