W. E. Ford — Rickardite, a New Mineral. 69 



Art. IV. — Rickardite, a New Mineral; by W. E. Ford. 



The new mineral to be described in this paper was first 

 brought to the writer's attention by Mr. T. A. Rickard of New 

 York. A qualitative examination proved that it contained 

 copper and tellurium, and no such combination having been 

 hitherto described, the mineral seemed worthy of investigation. 

 Through the courtesy of Mr. Rickard, sufficient material was 

 afterward obtained for making a quantitative analysis, the results 

 of which are given below. 



Rickardite occurs at Yulcan, Col., in the Good Hope mine 

 owned by Dr. Loui Weiss. The vein mineral is chiefly pyrite, 

 with which occurs native tellurium in unusually large masses, 

 some of which measure fully three inches across. Other asso- 

 ciated minerals are petzite, berthierite in imbedded prisms 

 resembling stibnite, and a greenish brown micaceous substance, 

 perhaps roscoelite. A large body of native sulphur also was 

 found in the vein. Rickardite itself occurs in small lense-shaped 

 masses, generally rather intimately associated with native tellu- 

 rium. 



The material for analysis was broken up and carefully gone 

 over by hand to free it from any adhering gangue and only 

 perfectly clean and homogeneous fragments were used. The 

 method of analysis was simple. The powdered mineral was oxi- 

 dized by nitric acid, which was subsequently removed by 

 evaporation with sulphuric acid. To the strong sulphuric acid 

 solution a liberal amount of hydrochloric acid was added and 

 then sulphur dioxide gas was led into the solution, which pre- 

 cipitated the tellurium in metallic form. This precipitate was 

 filtered onto a Gooch crucible, dried in the air bath at 100° C. 

 and then weighed. In the filtrate copper was precipitated by 

 hydrogen sulphide and determined as cuprous sulphide by 

 igniting in a stream of hydrogen. Careful tests were made for 

 gold, silver, lead, selenium, sulphur, arsenic and antimony with 

 only negative results. 



The analysis follows : 



I. 



Cu= 40-68 



Te= 59*36 59-06 59'21 -4737 = 2'93 



I. II. Average. Atomic ratios. 



Cu= 40-68 40-81 40-74 -6469 = 4-00 



Total 100-04 99-87 99-95 



These results give the ratio Cu : Te=4*00 : 2*93, or very 

 nearly 4*00 : 3*00, and the formula for rickardite therefore is 

 Cu 4 Te, . This gives as the theoretical composition of the 

 mineral, Cu = 40*51 ; Te= 59*49, which agrees very closely 



