180 G. J. Brush on Durangite. 
streak, cream yellow ; lustre, vitreous. Cleavage distinct in 
two directions, corresponding to two of the planes of the crys- 
tals at an angle of 110° 10’, according to measurements by Mr. 
J. M. Blake, who makes the crystallization monoclinic. (See 
note on the crystallization of the mineral, at the close of this 
article.) Hardness =5; specific gravity =3°95—403. 
When treated in the closed tube the mineral blackens ata 
moderate temperature, but regains its color on cooling; ata 
higher heat it fuses easily to a yellow glass and gives a faint 
white sublimate ; this sublimate proved to be volatile, and the 
glass appeared dimmed from corrosive action, Not the least 
trace of moisture was perceptible in the closed tube. In the 
— tube the same reactions were observed, with the addition 
at blue litmus paper was reddened when inserted in the upper 
end of the tube. On charcoal fuses readily, and in R. F. gives 
a strong arsenical odor and coats the coal with a faint white 
volatile sublimate. With soda the arsenical odor is more mark- 
ed, but in R. F. the assay affords no reducible metal. When 
fused with dry carbonate of soda and charcoal powder in a ma- 
trass yields a metallic ring of arsenic ; with borax and salt of 
phosphorus it gives only a reaction for iron, while with soda it 
yields a manganese-green. In the forceps, fuses with intumes- 
cence at 2 and gives a strong soda flame. 
_The mineral is only partially attacked by chlorhydric and 
nitric acids, but is completely decomposed by sulphuric acid, 
with evolution of fluohydric acid. A qualitative examination 
showed the presence of arsenic acid, alumina, iron, manganese, 
soda, lithia and fluorine. Search was made for other metallic 
acids, as well as for the rarer earths and metals, with a nega- 
i result; it also proved to be free from phosphoric acid and 
chlorine. 
num vessel etched glass with great readiness and distinctness. 
The following results were obtained : 
L 0: ri. 
Arsenic acid, _._____. a Sot ee 
Alumna,” ea oes 3009 =. 
Ferric oxyd, 2. 4°78 1°44 5-06 cae 
Manganous oxyd,---. 130 030 1°28 
oda 11°66 B01 2 6s: 11°86 
Lithia, 0-8 3 asa 0°70 
