70 W. & Ford — Rickardite, a New Mineral. 



with the analytical determinations. Kickardite is therefore 

 not only a new mineral but also a new type of telluride, for no 

 such four to three relation between metal and tellurium has 

 hitherto been noted in the group of tellurides. The mineral 

 may be regarded as consisting of one molecule of cuprous 

 telluride and two of cupric telluride, Cu 2 Te.2CuTe. 



Rickardite has an unusual and beautiful purple color, which 

 rivals in intensity the deepest purple tarnish ever seen on chal- 

 copyrite or bornite. The color, however, in the case of Rick- 

 ardite is not due to any tarnish, for it shows on a fresh fracture 

 and the powder of the mineral, even when ground very fine, is 

 of the same deep color. The mineral is massive in character 

 with an irregular fracture. Its hardness is 3*5 and its specific 

 gravity was determined as 7*54. It is fusible at 1 and gives a 

 pale azure blue flame color tinged in the outer parts with green. 

 Alone on charcoal before the blowpipe it gives a white coat- 

 ing of Te0 2 and fuses to a brittle globule of copper telluride. 

 Fused with sodium carbonate and borax on charcoal it gives a 

 coating of Te0 2 and a brittle globule of telluride, yielding only 

 with considerable difficulty a malleable globule of copper. 

 Roasted in the open tube the mineral fuses to a semi-transparent 

 mass of brown color, which is apparently some combination of 

 the oxides of tellurium and copper, and only a faint sublimate 

 of Te0 2 is formed on the walls of the tube. Heated in the 

 closed tube it fuses and undergoes no further change. Heated 

 in concentrated sulphuric acid it gives the characteristic reddish- 

 violet color of tellurium. When dissolved in nitric acid, the 

 solution neutralized with ammonium hydroxide gives the deep 

 blue color of copper. 



It is a pleasure to name the mineral Rickardite after Mr. T. 

 A. Rickard, the editor of the Engineering and Mining Journal 

 of New York, who obtained the material for investigation and 

 supplied the data as to its occurrence. Thanks are also due Dr. 

 Weiss of the Good Hope mine, who has been careful to secure 

 all specimens which might be of scientific interest. In con- 

 clusion, the writer wishes to express his indebtedness to Prof. 

 S. L. Penfield for his constant advice and assistance during the 

 preparation of this article. 



Sheffield Laboratory of Mineralogy, 



Yale University, New Haven. 



