414 Koenig — Neio Species Melanochalcite and Keweenawite. 



On the face of this result the establishment of a new species 

 would seem indicated. But as I have expressed myself (1. c), 

 the higher ratios of these copper arsenides are either down- 

 right mixtures (grain very fine) or they pertain of the nature 

 of alloys and hence all ratios are possible. In order to throw 

 a little more light on this subject, a long sliver was knocked 

 off the type specimen. On this sliver the mixture of two 

 substances was discernible. The sliver was broken into three 

 fragments and in each the copper was determined. 



a (0-5063 gram) gives Cu^S = 0*4836 per cent Cu = 76*2 

 /3 (0-500 gram) " " =0-4743 '' Cu = 75*76 

 y (0-506 gram) " " = 0-5097 " Cu = 80-10 



These differences would seem to bear out my statement. A 

 straight ratio marks an accident rather than a necessity. In 

 speaking of mixtures like these, it may perhaps be well to use 

 the term mohawk-algodonite^ as distinguished from true 

 algodonite. 



d. Mr. Rogers, another of ray students, collected a specimen 

 which did not quite correspond to anything I had seen before. 

 It was much tougher than the preceding specimen. A frag- 

 ment weighing 0-391 gram was dissolved and the copper 

 determined. Arsenic by difference. Nothing insoluble. 

 Cu,S = 0-4208, Cu = 0-3361 = 85-9 

 As = = 14-1 



100-0 

 Ratio 7-25 : 1 



It must be classified as mohawlc-whitneyite. 



e. Genuine Algodonite from the Champion Mine^ on the 

 South Copper Range. 



I am indebted to Dr. L. L. Hubbard, the Superintendent, 

 for the specimen. It presents a piece weighing about 400 

 grams, through which a drill-hole passes. The specimen was 

 encountered on a cross vein, very narrow, similar to the occur- 

 rence at the Mohawk mine. The metallic mineral is inti- 

 mately mixed with calcite. The fresh fracture is steel grey. 

 Several fragments were digested with dilute HCl. The residue 

 carefully washed and dried weighed 0*1968 grams. This quan- 

 tity was dissolved in HJ^Og and boiled nearly to dryness in 

 order to bring all the arsenic to the form HgAsO^. Only a 

 trace of white insoluble material (quartz) was observed. 

 0-0683 Mg^ASjO, = 0-0328 As 

 0-2063 CuO ' = 0-1645 Cu 



Hence Cu = 83-53 



As = 16-55 Cu : As = 5*96 : 1 



100-18 



