148 



GEOLOGICAL RECONNOISSANCE 



represent the composition of a fair average-specimen of the whole of the 

 ore brought out from this mine. The ore No. 1, contains, occasionally, 

 cavities in which small yellow crystals of blende (sulphuret of zinc) are 



found. 



Although of comparatively rare occurrence at this locality, large 



crystals of blende are occasionally met with, sometimes imbedded in dolo- 

 mite and surrounded by masses of flesh-colored, crystallized smithsonite, 

 (carbonate of zinc), and pearlspar. Crystals of smithsonite are abundant; 

 they are either found in the small veins traversing the dolomite (No. 32), 

 or forming the outer layer of irregular masses of ore, imbedded in red 

 clay; the crystals are of pale yellow, pale red, or flesh-color, rough on the 

 exterior, frequently possessing curved faces. A few hand-specimens pre- 

 sented the appearance of a brecciated rock; here, angular fragments of a 

 light reddish-gray, very close-textured dolomite (?) of splintery fracture, 

 were imbedded in a matrix of greenish-gray, coarser grained dolomite, 

 intermixed with flesh-colored crystals of smithsonite. 



The great mass of the ore occurs imbedded in red, feruginous clay, in 

 more or less rounded, irregular pieces. These pieces frequently consist 

 of three distinct layers: the outer one is formed of well-developed crys- 

 tals of pure smithsonite; then follows a layer of amorphous smithsonite, 

 possessing the physical properties of the above described ore, No. 1, which 

 passes gradually into a very soft amorphous mass of the composition 

 given in No. 2, and which is nothing but the same mineral constituting 

 the second layer, intermixed with some clay and other impurities. Its 

 color is from cream-color to brownish-yellow; it is easily scraped with a 

 knife, yielding a cream-colored powder. 



No. 1. Massive, amorphous, carbonate of zinc. 



Composition dried at 230 deg. F: 



Clay, and silicia '• 18.805 



Carbonate of zinc 75.474 



« « lime 0.364 



" mncrnfisia. trace 



" " magnesia 



Peroxide of iron, and alumina 1.771 



Water, and loss 3 - 586 



100.000 

 The air-dried ore lost 0.69 per cent, of moisture at 230 deg. F. 

 The carbonic acid in the carbonates of zinc and lime amounts to 26.685 

 per cent.; a separate experiment, on treating the pulverized mineral with 

 hydrochloric acid in a carbonic acid apparatus, gave 26.881 per cent. 

 Some of the iron was probably in the state of proto-carbonate. 



