APPENDIX. 325 



FORSTERITE. (See Vol. I. p. 214.) 



Its cleavage, perpendicular to the axis, is very distinct. Hardness 

 = about 7-0. 



FOWLERITE. (See Manganese Spar.) 

 GANSEKOTHIG-ERZ. 



Mammillary. Color yellow or pale green. Lustre resinous. Frac- 

 ture conchoidal. Translucent. Shining, with a white streak. Hard- 

 ness =2-0. . .3-0. 



Before the blow-pipe, it emits copious fumes of arsenic, and fuses into 

 a blackish scoria ; when the heat is continued on charcoal, the scoria 

 melts, and yields a button of silver, but the slag contains metallic iron, 

 which strongly affects the magnet. It is supposed to be an arseniate of 

 silver and iron. 



It occurs mostly in the mines of Clausthal in the Hartz, where it is of 

 some importance as an ore of silver. It is likewise met with in Corn- 

 wall, and at Allemont in Dauphiny. 



GlGANTOLITE. 



A mineral composed of alumina, lime and iron, found in the granitic 

 rocks of Tamela in Finland. 



GREEN VITRIOL. 



Massive, granular. Lustre dull. Color sometimes a fine green, 

 more often of a greyish green. 



1. It dissolves readily, and without alteration, in muriatic acid; slow- 

 ly in ammonia, and rapidly in carbonate of ammonia. 

 2. Analysis. 



Ty BERTHIER. 

 Deuloxide of copper 66-20 



Sulphuric acid 16-60 



Water 17-40 



3. It is found in Mexico. 



HUMBOLDTILITE. 



In right square prisms. Lustre vitreous. Semi-transparent. Frac- 

 ture uneven. Color yellow, or yellowish grey. Hardness = 5-00. Sp . 

 gr. =3-104. 



VOL. ii, 28 



