A REVIEW OF THE AMORPHOUS MINERALS 527 



hydrocuprite may be used. Werner considered rothkupfererz and 

 zeigelerz as co-ordinate. Beudant used the name zigueline as a 

 species name for cuprous oxid. Hydrocuprite was described by 

 Genth 1 as an orange-yellow to orange-red, amorphous raglike coat- 

 ing on magnetite from Cornwall. The same substance has been 

 noted by Lacroix on cuprite from Chessy, France, and by Sand- 

 berger, mixed with cuprite, from Schapbach, Baden. According 

 to Schaller 2 the supposed vanadium ocher from Lake Superior is 

 hydrocuprite (or possibly cuprite) . 



I have observed what I consider to be amorphous cuprous oxid 

 in specimens from the Lowell mine, Bisbee, Arizona; the Poderosa 

 mine, Collahuasi, Chile; and an unknown locality. The hydro- 

 cuprite occurs as a massive brick-red mineral associated with 

 cuprite. Under the microscope it appears as an orange-colored, 

 almost opaque substance in contrast to the dark-red translucent 

 cuprite. No very satisfactory optical tests can be made on account 

 of the opacity, but in a few spots the orange-colored mineral is 

 isotropic as well as the cuprite. 



On account of the optically isotropic character of both of these 

 minerals the closed-tube test may prove useful. Hydrocuprite 

 contains water, but it is not a definite hydrate, as the name implies. 



Melaconite. CuO(H 2 0) a; (tenorite in part, melanochalcite) . — ■ 

 Dana united the crystalline tenorite and amorphous melaconite 

 under the name tenorite, but they should be separated. Crystal- 

 line tenorite is a very rare mineral, known only from Vesuvius, 

 Cornwall, and Keweenaw Point, Michigan, but the amorphous 

 melaconite is a fairly common mineral in the oxidized zone of 

 copper mines. It is a black, massive mineral and occasionally 

 occurs in colloform crusts. In fragments it is black and opaque, 

 but is usually translucent brown and isotropic on the thin edges. 

 In addition to cupric oxid and water melaconite also contains silica, 

 the carbonate radical, and often manganese oxid. 



Melanochalcite, described by Koenig as a copper salt of silico- 

 carbonic acid, is undoubtedly melaconite. Kraus and Hunt 3 



1 Preliminary Report on the Mineralogy of Pennsylvania, Pennsylvania Second 

 Geol. Surv., 1875, p. 46. 



2 Am. Jour. Sci. (4), XXXIX (1915), 404- 3 IMd., (4), XLI (1915), 211-14. 



