129 
% 
GENERAL MINERALOGY OF THE DISTRICT. 
composition of kaolin. Contrary to the opinion of Penrose, the kaolin appears 
to be strictly confined to the zone of oxidation, and is probably formed by the action 
of sulphuric acid on aluminous minerals. 
Clirysocolla .—Occurs as a product of oxidation of tetrahedrite on level 7 of 
the Ironclad mine and may probably be found in small quantities at many other 
places. 
Morendte {?), chloropal (?).—Within the oxidized zone a soft dark-green to 
black substance is of fairly common occurrence as the filling of seams and narrow 
veins. Upon being dried it assumes a light yellowish-brown color and proves to 
be chiefly a hydrous ferric silicate, possibly corresponding in part to chloropal and 
in part to the newly established species morencite. rt It was first observed by 
Penrose b from the Ida May mine, and has been noted by us from the Portland, 
Vindicator, and Deadwood mines. Hillebrand found the mineral from the Ida 
May mine to consist of 41.80 per cent Si0 2 , 37.20 per cent Fe 2 0 3 , 19.90 per cent H 2 0, 
and 1.10 per cent CaO, etc. Smaller amounts of carbonates and phosphates are 
often present. 
HYDROCARBONS. 
Coal .—At several places the breccia contains inclusions of coaly material, 
evidently formed by carbonization of vegetable remains carried down from the 
surface at the time of the volcanic eruptions. The character and significance of 
these occurrences have been discussed on page 31. 
aLindgren, W., and Hillebrand, W. F., Min erals from, the Cliitou-Morenci district, Arizona: Am. Jour. Sci., vol. 18, 
December, 1904, p. 455. 
t Op. cit., p. 122. 
