+ 
152 GEOLOGICAL RECONNOISSANCE 
in ferruginous clay. The most valuable ore is a compact, cellular, sub- 
crystalline smithsonite, of brownish-white and grayish-white color, surface 
botryoidal, resembling, in its general appearance, the. principal ore from 
the Koch mine, (analysis No. 5); the cavities are partially filled with clay. 
The subjoined analysis, No. 8, represents the composition of this ore. 
The sample has been carefully selected, so as to approach as near as 
possible to the composition of a fair average-specimen. ; 
Well developed crystals of smithsonite, abundant in the mines of Law- 
rence county, appear to be entirely wanting, as are also the thin veins of 
pearlspar, traversing the dolomite. In theirstead, the dolomite is frequently 
found incrusted with a compact mass of a pale brownish-white, or 
greenish-white carbonate of zinc, with ‘botryoidal surface, consisting of a 
succession of concentric layers, the whole deposit having sometimes a 
thickness of upwards of half an inch. Its hardness is between 4 and 5; 
streak white; translucent; brittle; fracture splintery; heated in a glass-tube, 
closed at one end, gives no water, but turns opaque and yellow, after 
cooling opaque and white; on charcoal before the blowpipe, gives the 
reactions of oxide of zinc. Its composition is given in No. 9. Interven, 
ing between this mineral and the dolomite, a thin layer of crystallized 
quartz, of brownish color, is frequently met with; the quartz in the sub- 
joined analysis (No. 9), is probably derived from an intermixture of this 
layer with the carbonate of zinc. 
No. 8. Brownish-white, cellular, smithsonite. 
Composition, dried at 212 deg. F: 
Clay, sand, and silica .-+-+s sees cues eeeeeee 7.523 
Oxide OE SVEN Cs esha ah aca santas Siecsh, weg AR Sea eosr aoe 59.770 
Peroxide of iron, with trace of manganese. - 3.507 
Oxide of cadmium. +++ +. se ce eee e cree eeens 0.486 
(OA dicw.e eatee Ss BASE HERRERA Ra 0.066 
ee “ copper: Seb ee meee r ere eeseeene trace 
TAME. Sevwsnscee we eaawi ees wa awe we 0.466 
Magnesia eee ee ne oe ae ee Lore ea a ee a trace 
Carbonic acid, water, and loss.+++++++eeee- 28.182 
100.000 
The air-dried ore lost 1.84 per cent. of moisture at 212 deg. F. 
59.77 per cent. of oxide of zinc are equal to 47.97 per cent. of metallic 
zinc. 
The iron has been represented as peroxide, because the greater part of 
¥ 
