22 F. A. Canfield — Miner alogical JVotes. 



mentioned by Professor Penfield. This depression has the 

 effect of a double face, each half of which is striated by lines 

 lying nearly parallel with one side of the rhombic face and 

 meeting the lines of the adjacent face at an angle of about 90 

 degrees, at the bottom or center line of the depression. These 

 lines may have been caused by interruptions during the growth 

 of the crystal. Some of the crystals are twinned spinel fash- 

 ion, and on some of these the dodecahedral faces are depressed 

 and striated. A very few of the crystals are simple octahe- 

 drons, and a few show faces of the cube in combination with 

 the other forms. The type crystals of argyrodite do not show 

 the depressions and striations. 



When in Colquechaca, the writer purchased several speci- 

 mens which are similar to those described by Messrs. G. T. 

 Prior and L. J. Spencer, in their paper on " Stanniferous 

 Argyrodite from Bolivia," etc.* The crystals do not show 

 the striated depressions. Many are spinel twins. These crys- 

 tals have not been analyzed. One specimen is made up of 

 brilliant black rhombic dodecahedrons with but few traces of 

 the octahedron. The angles are sharp with no signs of twin- 

 ning. It is probably argyrodite. 



In 1889, the writer identified his crystals by a specimen in 

 the British Museum Collection, which was labeledf "brongni- 

 ardite " from Aullagas, Bolivia. Damour described this min- 

 eral as coming from Potosi. It is safe to say that none of 

 these minerals was found in the mines near the city of Potosi. 

 The Department of Potosi covered more than 10,000 square 

 miles and included Porco and Colquechaca, and in this sense 

 the locality as given was correct. It is more probable that 

 the specimens of the so-called brongniardite of A. Damour 

 and Louis Saemann were carried to the city of Potosi from 

 Porco or Colquechaca. 



Dover, New Jersey. 



*Min. Mag., xii, 5, 1900. 



f Messrs. Prior and Spencer (1. c.) have proved this specimen to be stan- 

 niferous argyrodite. 



