190 ALUMINA. 



AXINITE. 



Triclinic. In acute edged oblique rhomboidal prisms ; 

 P : M = 134^ 40, P : f = 115° 5, M : T = 

 135 ' 10'. Cleavage indistinct. Also rarely 

 massive or lamellar. 



Color clove brown; differing somewhat in 

 shade in two directions. Luster vitreous. Trans- 

 parent to subtranslucent. Brittle. H=6'5— ■ 

 7. Gr = 3-27. Pyro-electric. * 



Composition : silica 45, alumina 19, lime 12*5, peroxyd of 

 iron 12*25, peroxyd of manganese 9, boracic acid 2*0, mag- 

 nesia 0*2. In another specimen 5*6 per cent, of boracic 

 acid were found. Before the blowpipe fuses readily with in- 

 tumescence to a dark green glass, which becomes black in 

 the oxydating flame. 



Dif. Remarkable for the sharp thin edges of its crystals, 

 and its glassy brilliant appearance, without cleavage. The 

 crystals are implanted, and not disseminated like garnet. In 

 one or all of these particulars, and also in blowpipe reaction, 

 it differs from any of the titanium ores. 



Obs. St. Cristophe in Dauphiny, is a fine locality of this 

 mineral. It occurs also at Kongsberg in Norway, Normark 

 in Sweden, and Cornwall, England ; also Thum in Saxony, 

 whence the name Thummerstein and Thumite. 



In the United States, it has been found at Phippsburg in 

 Maine, by Dr. C. T. Jackson. 



iolite . — Dichroite, Cordierite. 



Trimetric. In rhombic and hexagonal prisms. Usually 

 occurs in six or twelve-sided prisms, or disseminated in 

 masses without distinct form. Cleavage indistinct; but 

 crystals often separable into layers parallel to the base. 



Color various shades of blue ; often deep blue in the di- 

 rection of the axis, and yellowish-gray transversely. Streak 

 uncolored. Luster and appearance much like that of glass. 

 Transparent to translucent. Brittle. H=7— 7-5. Gr = 

 2-6—2-7. 



Composition of a specimen from Haddam, Ct. : silica 48*3, 



What is the form and color of axinite ? What characters distinguish 

 it ? Why was it so called 1 What are the forms of iolite ? What 

 are its colors, appearance and hardness ? 



