^^89.J Mmeralogy and Petrography. 815 
a cleavage parallel to 00 P5) . The axial ratio is ^ : /; : ^— 1.2138 : i 
: 5862. y3 = 85°. The boracite is found in carnallite layers. It 
occurs in small colorless or light green crystals that are combinations 
of the cube and tetrahedron, with occasionally dodecahedral and other 
(if),-(-)..-(40) 
Rare Miner a\s.-~ Ma zapiVih-, described by Dr. Konig,24 proves 2' 
) be a calcium-iron arseniate, with the composition : 
AsX), SUO, 1\(). Fe^O, CaO H,0 
)mbic system, has a prismatic habit, and a 
-Uraninite.—lxx a preliminary notice, Mr. 
combination as to yield the free gas upon treatment with an acid. He 
adds also that all specimens of this mineral examined, with the excep- 
tion of one from Bohemia, are found to contain thoriaor zirconia. 
Plattncrite. the rare lead di -oxide, is described by Wheeler,^^ and by 
Messrs. J. ]). and K. X. Hawkinses as occurring in a lead mine in 
Shoshone count)-, Idaho. The specimens examined are black. They 
fusibilit}^ of 2. Analyses show that 
the mineral 
91 and 96.63 percent, of PbO^. 
Gyrolite occurs as a colorless, fibrous layer lining the walls c. „ 
apophyllite vein at the New Almaden Quicksilver Mine, in Californic 
Its composition, as determined by Prof. Clarke.^^ is : 
SiO, AI.P3. Fe^O., CaO K./) Xa/) F H,0 
52-54 .71 29.97 1.56 .27 .65 14.60 
\MER. Naturalist, Feb., 1889, p 
'roc. Acad. Nat. Sci., Phila., 45., i£ 
^mer.Jour. Set.. Oct., i88g, p. ^20, 
