452 S. L. Pen field — Sulphostannate of Silver from Bolivia. 



better crystals of the Freiberg argyrodite than those originally 

 described had been examined, and the results had shown that 

 they were isometric and tetrahedral. These conclusions have 

 since been published.* The forms m and o of Weisbachf are 

 regarded as the dodecahedron (110),/" and k as the tetrahedron 

 x(lll), \ and v as the negative pyramidal-tetrahedron x(311) 

 — 2^2-. Argyrodite being isometric it is evident that the Bo- 

 livian mineral is not a new species and the name caniieldite is 

 therefore withdrawn. For the sake of simplicity it is a satis- 

 faction to have the Bolivian mineral identical with that from 

 Freiberg, and it is regretted that the isometric character of 

 argyrodite was not made known before the publication of the 

 canfieldite paper. It was hoped that by the present time some 

 definite information could be given concerning this new occur- 

 rence of argyrodite, but as yet no data have been received 

 other than that it is a well known silver ore in the mines at 

 Potosi. 



There has also recently come into the authors possession, 

 through the kindness of Mr. Wm, E. Hidden of New York, a 

 specimen from La Paz, Bolivia, which was supposed to be 

 argyrodite. Its total weight was a little over seven grams and 

 it consisted of a few attached octahedrons, modified by dode- 

 cahedron planes, the largest crystal measuring 13 mm in axial 

 diameter. The only visible impurity was a very little metallic 

 silver in wire form, deposited in a few places on the outside of 

 the crystals. The mineral is almost identical with argyrodite 

 in all of its physical properties. The luster is brilliant metal- 

 lic. Color black with the same bluish to purplish tone 

 observed on argyrodite. The fracture is irregular to small 

 conchoidal. Yery brittle. Hardness 2^-3, specific gravity 

 6*276, that of argyrodite from Bolivia being 6*266. Heated be- 

 fore the blowpipe on charcoal at the tip of the blue cone the min- 

 eral fuses at about 2 and yields a coating of the mixed oxides 

 of tin and germanium. This is white to grayish near the 

 assay, tinged on the outer edges with yellow. By continued 

 heating a globule of silver results but this is covered by a 

 scale or coating of tin oxide. If the coating on the charcoal 

 is scraped together and fused in the reducing flame with 

 sodium carbonate globules of tin are formed. In the closed 

 tube sulphur is given off and at a high temperature a slight 

 deposit of germanium sulphide, which fuses to globules, is 

 formed near the assay. In the open tube sulphur dioxide is 

 given off but no sublimate is deposited. 



The following method was adopted for the analysis. The 

 mineral was oxidized by concentrated nitric acid and the excess 



* Jahrb. 1 Min., 1894, i, p. 98. 



f Compare figure in Dana's Mineralogy, sixth edition, p. 150. 



