PHYSIOGRAPHY. 91 



Brucite. 



Secondary form. In very short prisms, apparently hav- 

 ing all the edges and solid angles replaced so as to oblite- 

 rate the lateral and terminal planes. The secondary ter- 

 minal planes much rounded ; the most distinct crystals 

 affording angles over the summit of between 130 and 140 

 with the common goniometer. 



Cleavage parallel with M, M' indistinct ; that parallel 

 with P very indistinct. 



Lustre vitreous, to resinous. Color yellow, brown and 

 red. Transparent . . . translucent. 



Hardness = 6-5. Sp. gr. = 3-199. 



Compound Varieties. Massive : composition granular, 

 of various sizes of individuals. 



1. It is fused with difficulty before the blow-pipe. It loses its color 

 almost entirely, becomes opake, and shows traces of fusion on very thin 

 edges. The brown and grey varieties act upon the magnetic needle, 

 where the double magnetism is employed. 

 2. Analysis. 



By D'OnssoN. By SEYBERT. , 



Silica . . 38-00 . . 32-666 



Magnesia . . 54-00 . . 54-000 

 Oxide of iron . 5-10 . . 0000 



Peroxide of iron . 0-00 . . 2 333 



Alumina . 1-50 . . 0-000 



Potash . 0-86 . . 0-000 



Fluoric acid . 0-00 . . 4-086 



Water . 0-00 . . 1-000 



3. Brucite is found disseminated through Calcareous Spar, associated 

 with Hornblende, Spinel and Mica. 



4. It occurs at Ersby in the parish of Pargas in Finland, where it was 

 first discovered : but its most abundant localities are in the U. States, 

 in the adjoining counties of Sussex, (New-Jersey.) and Orange, (New 

 York,) where it exists under the circumstances above described, and also 

 accompanied by Spinel, and rarely by Pyroxene and Bronzite. In 

 Sussex county, it is particularly abundant at Newton ; and in Orange 

 county, at Amity and Edenville. 



