THE MINERALS OF IDAHO 395 



COPPER PITCH ORE (504a) 

 MELANOCHALCITE 



Impure hydrated copper silicate, vari- Amorphous, 



able amounts of iron, manganese, 

 zinc, etc. 



A dark-brown to light-brown or black impure copper silicate 

 containing variable amounts of iron and other substances has long 

 been known by the old German name kupferpecherz or copper 

 pitch ore. This is commonly regarded as an impure variety of chryso- 

 colla, although specimens of doubtful nature and homogeneity have 

 been described from different localities and have been given specific 

 names, such as melanochalcite. The material appears very unlike 

 the fine green opal-like chrysocolla with which it is often associated 

 and, since it is a common ore mineral in Idaho it is here considered 

 separately as a subheading under chrysocolla. The principal Idaho 

 occurrences of this material are as follows. 



ADAMS COUNTY 



Copper pitch is a common ore mineral in the copper deposits of 

 the Seven Devils district where it occurs intimately associated with 

 chrysocolla, rarely in alternating concentric layers with the green 

 chrysocolla, which it resembles in all respects except color. 5 Much 

 of the copper pitch from this district is dead black in color, opaque 

 and almost lusterless. Much of what has been described from here 

 as melaconite is probably impure silicate. A specimen of the sup- 

 posed melaconite from the Peacock claim is hard and compact. 

 A small portion, subjected to a very crude analysis gave the following 

 results: 



Analysis of "melaconite" from Seven Devils 



(E. V. Shannon, analyst) 



Per cent. 



Silica (Si0 2 ) 32.4 



Ferric iron (Fe 2 3 ) 12. 8 



Copper oxide (CuO) 38. 6 



Manganese oxide (MnO) 2. 9 



Zinc oxide (ZnO) 3.4 



Water (H 2 0) by difference 9. 9 



Total 100. 



This material is doubtless copper-pitch rather than melaconite. 

 A specimen from the Peacock dump shows abundant pitchlike dark 

 brown material forming broad layers surrounding masses of bornite 

 and grading outward into broad bands of green chrysocolla. Speci- 

 mens from the quartz vein on the Queen claim show considerable 

 masses of similar material in quartz containing residual masses and 



« D. C. Livingston and F. B. Laney. Idaho Bur. Mines and Geol., Bull. 1, pp. 37, 67, etc., 1920. 



