PHYSIOGRAPHY. 227 



Gehlenite Gibbsite. 



rEHLENITE. Pyramidal Dystome- Sp ar. 



Primary form. A right square prism. 



Cleavage, in traces, parallel with the base. 



Lustre resinous, inclining to vitreous. Color, different 

 hades of grey, mostly yellowish ; none of them bright. 



Opake. Sometimes faintly translucent on the edges. 



Brittle. Hardness =5-5 . . . 6*0. Sp. gr. =3-029. 



1. Before the blow-pipe, it fuses only in thin splinters. In borax, it 

 very slowly dissolved. It gelatinizes in heated muriatic acid. 



2. Analysis. 



By FUCHSK By KOBELL. 



Alumina . . 24-80 . .. . 21-4 



Silica . . 2964 . . . 31-0 



Lime . . 35-30 . . . 37-4 



Oxide of iron . 6 56 ... 4-4 



Magnesia . . 0-00 ... 3-4 



Water . . . 3 30 ... 20 



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

 Tyrol, along with Calcareous Spar. 



3IBBSITE. Staphyline Wavelline-Spar. 



Irregular stalactites ; tuberose masses. 



Structure fibrous, the fibres radiating from the centre. 



Lustre faint. Color greenish or greyish white. Trans- 

 ucent. 



Hardness =3*0 . . . 3'5, but easily reduced to powder. 

 Sp. gr. =2-4. 



1. Before the blow-pipe, it whitens, but is infusible. 

 2. Analysis. 

 By TORREY. 

 Alumina ..... 64-8 



Water 34-7 



3. It is found in very small quantity only, disseminated through a bed 

 of Limonite, at Richmond, (Mass.) 



