-±26 Palache — Notes on Tellurides from Colorado. 



While little weight can be attached to a comparison based 

 thus on a defective analysis, still it seems clear that the mate- 

 rial studied differs but little from the typical goldschmidtite in 

 composition. On the other hand, while the gold content is 

 high when compared with that of the theoretical AuAgTe 4 , it 

 should be clearly remembered that no sylvanite with exactly 

 that composition has been as yet analyzed, the gold content 

 actually found varying from 25 - 87 per cent to 29*35 per cent 

 with proportionately varying silver content. These results 

 seem to show conclusively that the ratio of gold to silver in 

 sylvanite may vary considerably from the theoretic proportion 

 of 1 : 1, without affecting the physical characteristics materially, 

 and it is a question whether it is advisable to attempt to estab- 

 lish species based upon these variations of composition. 



Note by Professor W. H. Hobbs. — In view of the results of 

 the investigation by Dr. Palache, above detailed, it seems 

 proper for me to say that the name goldschmidtite should be 

 withdrawn from mineralogical literature as representing a dis- 

 tinct mineral species. Dr. Palache's study shows that gold- 

 schmidtite can be referred to the same set of axes as sylvanite, 

 of which it represents a peculiar type. This being true my 

 analysis, which had to be made on an extremely small amount 

 of material, must contain a large error. The method used was 

 the oxidation of the tellurium on charcoal, weighing the but- 

 ton of combined silver and gold, and, after solution of the 

 silver, weighing the gold in the form of powder. The danger 

 of this method lies in the possibility that tellurium will not 

 be completely eliminated and that some silver will oxidize. 

 The button obtained was, however, bright and apparently 

 freed from tellurium. I regret that material is not now avail- 

 able for a second analysis, yet in view of Dr. Palache's crystal- 

 lographic study of better material, checked as it has been by 

 analysis, no course is open to me but to discredit the results of 

 my analysis. 



3. Hessite Crystals from Colorado. 



A specimen of well-crystallized hessite from Boulder Co., 

 Colorado, has been recently acquired by the Harvard Mineral 

 Cabinet from Mr. G. B. Frazer. A description of this speci- 

 men is here offered because the crystals present certain interest- 

 ing peculiarities of habit and because so far as the author has 

 been able to discover no crystals of this mineral from the 

 United States have yet been figured. 



The specimen consists of a small fragment of bluish vein 

 quartz in one side of which is a drusy, quartz-lined cavity. 

 On the quartz walls of the cavity are eight or ten brilliant 

 hessite crystals, a millimeter or less in height, and two small 



