Genth.] ^-^ [March 18, 



"The bismuthine (bismuthinite Dana) in this mine is found : 



"1. As brilliant untarnished crystals. 



" 2. Crystals with a slight deposit of cassiterite on them. 



"3. With the cassiterite coating the bismuthine in concentric layers, 

 wood tin. 



"All wood tin, the bismuthine having been carried away. 



"You doubtless are familiar with the remarkable pseudomorphs of cas- 

 " siterite after quartz which received for a short time the name of stannite 

 "or silicate of tin from the late John Garby," &c., &c. 



I should mention also the very interesting observation of microscopic 

 crystals of cassiterite in the black zincblende of Freiberg, Saxony, de- 

 scribed by Dr. A. W. Stelzner, and Dr. A. Schertel (Jahrbuch fiirBergund 

 Hiittenwescn im Kouigreich Sachsen auf das Jahr, 1886). The cassiterite 

 in the variety "Nadelzinnerz" occurs associated with quartz crystals and 

 sometimes implanted in the same, in minute and microscopic crystals and 

 groups of crystals. Most of the forms are simple combinations of prisms 

 and pyramids, and have no resemblance with the Mexican specimens. 

 The whole occurrence indicates a simultaneous formation of the zinc- 

 blende and cassiterite. 



S. Hematite. 



Both localities, the Mina del Diablo, and that in the Catatlan mountains 

 from whicli the sands of Mr. Schlemm were obtained, furnished minute, 

 sometimes very perfect, crystals of hematite, occasionally grouped in the 

 form of "eisenrose." The crystals trom Mina del Diablo are larger, at 

 times from 2 to 3""" in diameter and have the basal plane oR more fully 

 developed. 



The crystals from the sands of Mr. Schlemm are very minute, and I am 

 indebted to Prof G. vom Rath for the following information :* 



Contrary to the general rule these very minute crystals, from 0.2r> to 

 1"™ in size show a holohedral development with the second hexagonal 

 prism a;P2, striated parallel to the basal edge, prominent. The second 

 pyramid §P2 (~ in Miller's mineralogy, ~ ; oR = 137° 49') dominates the 

 polar development of these crystals. As combinations appear a more 

 acute second pyramid f P 2 (n in Miller, n : oR = 118° 53'). R and 

 — ^R. oR appears from a mere point to a relatively large extension. 

 Iroublack, powder brownish red ; sliahtly magnetic. 



As already mentioned under cassiterite, that hematite is sometimes 

 found in part or wholly altered into cassiterite. 



* I have sent to Prof, vom Rath the crystals of hematite, above referred to, 

 also the peculiar psendomorphous crystals with mimelite composition and the 

 first specimens which I had received of the vanadinite and descloizite Irom 

 Oracle, In Arizona. He has taken such an interes^t in these occurrences that 

 he communicated the results of his in vestigations to the " Niederrlieinische Ge- 

 sellschait fUr Natnr und Heilkunde zu Bonn," at the meeting of January ILth, 

 1886, which have been published by this Society. In the following pages I shall 

 refer to these communications, as 1. c. 



