164 KANSAS UNIVERSITY QUARTERLY. 



inous luster, and has very much the appearance of gum arable. In 

 physical characters agrees very well with the description of schoetter- 

 ite, but is quite different in chemical composition. Mr. C. A. Wol- 

 faith, superintendent of the Dearborn mine, kindly furnished the 

 material for analysis. An analysis gave the following, which is the 

 mean of two determinations : AloO:^, (41.6(3) ; SiOi, 24.76 ; H9O, 33.58 ; 

 total, 100.00. Specific gravity = 1.94. The silica percentage is rather 

 high and the water percentage rather low for allophane, but it is much 

 nearer that mineral than any other, and so is referred to it with a query. 



Caledonite. Occurs in very small quantities as a green crystalline 

 coating, associated with linarite, aurichalcite, and cerussite ( with a lit- 

 tle unaltered galena), at the "Big Coon" mine. Galena. Heated in 

 the closed tube, becomes black and gives off water. Reacts for Pb, 

 Cu. and SO4. Soluble in nitric acid, leaving a white residue of lead 

 sulfate. Has been reported from but two or three localities in the 

 United States. 



CJirysocolla. This mineral occurs as thin seams of the characteris- 

 tic bluish-green color associated with other copper minerals at the "Big 

 Coon" mine, Galena. 



Cop'tdplte. A basic ferric sulfate, referred to copiapite, occurs as a 

 yellow crystalline incrustation on pyrite at Galena and at Cave 

 Springs, Mo., being especially abundant at the "Pilgrim" mine at the 

 latter locality, where it occurs on the walls of a cave-in. 



CoveUite. The sphalerite from the "Big Coon" mine is often 

 coated with a bluish-black substance, which is seen to penetrate the 

 cleavage faces for a considerable distance. This mineral it is thought 

 is covellite, as it agrees with it in physical characters and, as far as 

 can be determined, in chemical composition. It seems probable that 

 a metathetic reaction has taken place between zinc sulfid and copper 

 sulfate, thus: ZnS + CuS04 = CuSH- ZnSO-t. Such a reaction does 

 take place when sphalerite is heated in a closed tube containing a 

 solution of copper sulfate at a temperature of 200 degrees, as experi- 

 ments by the author show. Given sufficient time and favorable con- 

 ditions, may not this reaction have taken place without the high 

 temperature ? Exterior to the covellite is often malachite, which is a 

 further product of the decomposition of the covellite. Here, then, we 

 have covellite and malachite pseudomorphous after sphalerite. 



Cuprite. Cuprite was observed as a central core surrounded by 

 malachite, from which the latter was evidently formed. The cuprite, 

 it is believed, is also secondary, and probably has been formed from 

 chalcopyrite, which seems to be the only original copper mineral of 

 the reo-ion. This opinion is largely suppositious, as there is no evi- 



