358 W. H. Hobbs — Goldsekmidtite, a New Mineral. 



which it probably corresponds in composition. The fragments 

 of the breccia are, however, only loosely consolidated, so that 

 the specimen is crossed by numerous irregular cracks, the walls 

 of which are coated with chalcedony. 



The crystals of the mineral which is here discussed are 

 firmly attached to the chalcedony, so that great difficulty was 

 experienced in removing them without fracture, particularly 

 as they are possessed of a perfect cleavage. These crystals 

 have a rather long columnar habit with some tendency also to 

 elongated tabular forms with reference to a plane parallel to 

 this axis, and in one or two cases they were observed to have 

 the arborescent forms which have given the name " Schrifterz " 

 to the mineral sylvanite, and have been explained by twinning. 

 The largest individual observed was only about 5 ram in length 

 and those which I have succeeded in separating from the chal- 

 cedony of the walls would average hardly 2 mm in length, with 

 a thickness perhaps a third or a fourth as much. Examination 

 with the lens showed these crystals to be considerably modified 

 and without striation or other distortion, and, except for their 

 minute size, they are admirably suited to measurement. They 

 have a perfect cleavage following the plane of their tabular 

 development. They are seen to be often twins, the plane of 

 twinning following the columnar axis in a direction normal to 

 the cleavage. They are quite brittle and have a hardness of 

 about 2, since they will just scratch the surface of selenite. 

 The amount of material was not sufficient for a satisfactory 

 determination of the specific gravity, but the mineral's compo- 

 sition as recorded below, and the comparison of it with syl- 

 vanite and calaverite, make it probable that the specific gravity 

 is very near to 8*6. The luster of the mineral is bright metal- 

 lic and the color a silver white. The streak is dull, grayish 

 black. 



Chemical Composition. 



Examined on charcoal before the blowpipe, the mineral 

 readily fuses surrounded by the light bluish green flame which 

 is characteristic of tellurium, leaving on the coal a white coat- 

 ing of tellurium oxide. A yellowish white button of gold and 

 silver results from the fusion, as in the cases of sylvanite and 

 calaverite, though it is much less yellow than the button 

 obtained from the last mentioned mineral. No antimony, sul- 

 phur, or selenium could be detected. 



A portion of the specimen was broken up and by careful 

 and laborious picking out of the crystals and fragments of crys- 

 tals about one-tenth of a gram of nearly pure mineral was 

 obtained, which was analyzed and found to contain gold, silver, 

 and tellurium, in the following proportions, the tellurium 

 being estimated by difference : 



