GIBBSITE. 103 



Pyramidal or prismatic. P oo. P -f- oo or 

 P oo. Pr + oo. Pr + ar>. Cleavage, P oo 

 distinct, the other faces imperfect. 



Lustre resinous, inclining to vitreous. Colour dif- 

 ferent shades of grey, none of them bright. 

 Opake. Sometimes faintly translucent on the 

 edges. 



Brittle. Hardness = 5-5... 6-0. Sp. Gr. = 3-029. 



It is difficultly fusible before the blowpipe, and only in 

 thin splinters. Also in borax it is very slowly dissolved. 

 It gelatinises in heated muriatic acid. It consists, accord- 

 ing to FUCHS, of 



Alumina 24-80. 



Silica 29-64. 



Lime 35-30. 



Oxide of Iron 6-56. 



Water 3-30. 



It has been found on Mount Monzoni, in the valley of 

 Fassa in the Tyrol, along with rhombohedral Lime-haloide. 

 It was described by Professor Fc CHS. 



GIBBSITE. 



Gibbsite. TORREY. New York Medical and Physical 

 Journal. No. I. p. 63. 



Irregular stalactites, tuberose masses. 



Structure fibrous, the fibres radiating from the 

 centre. 



Lustre faint. Colour dirty greenish- or greyish- 

 white. Slightly translucent. 



Hardness a little above 3-0, but easily reduced to 

 powder. Sp. Gr. 2-400. 



It yielded to TORREY, alumina 64-8, and water 34-7. It 

 whitens before the blowpipe, but is infusible. Its locality 



