Genth.] -"t) [March 18, 



well adapted for soldering, notwithstanding the considerable quantities of 

 lead and arsenic which it contains. 



No. 4. The washings from the Catatlan mountains, which Mr. Klein- 

 schmidt received from Mr. W. Schlemm, are highly interesting. They 

 consist of a fine sand, the particles rarely over 1™™ in size. 



There were no lead ores present, but cassiterite, mostly in the red 

 variety, but also minute quantities of the yellow, interesting forms of 

 hematite and alterations of the same, a few crystals of topaz, many 

 minute crystals of durangite, quartz, etc. 



No. 5. The ores from Mina Varosa are exclusively ot the yellow va- 

 riety. 



No. 6. The Placer ores are both of the red and yellow varieties, the 

 former largely predominating, also pieces showing bands of the yellow 

 alternating with a brown variety. 



For comparison several other varieties of Mexican cassiterite were ex- 

 amined which were kindly presented by Messrs. Clarence S. Bement, 

 Joseph Wharton, Prof. Carlos F. de Landero, and Dr. Joseph Leidy, to 

 all of whom I am greatly indebted for their liberality ; I am also under 

 great obligations to Professors Gerhard vom Rath and George A. Koenig, 

 for generous aid rendered in the preparation of this paper. 



1. Cassiterite. 



As already indicated, cassiterite occurs in Mexico principally in two 

 varieties, the most abundant ot which has a red color, while the other is 

 yellow. 



a. Red variety. — Occurs in various shades of red, from bright hyacinth 

 red, brick-red to brownish red, to brown and brownish-black. The pow- 

 der is from pale to brownish brick-red. The general appearance of the 

 red cassiterite proves that the dioxide of tin was in solution from which it 

 has been deposited upon whatever substances it came in contact with, so 

 that numerous imitative shapes were produced. Thus, we find it as in- 

 crustations in plate like masses which formed upon quartz or porphyry, 

 or in reniform, mammillary, or botryoidal aggregations, frequently in per- 

 fect stalactites, which are sometimes not over 0.5™"" in length, often hol- 

 low, radiating from the centre, often in forms resembling sponges, roots, 

 clubs, &c. ; sometimes granular and compact, especially larger masses, 

 which closely resemble compact hematite, towards the exterior frequently 

 assuming a fibrous structure which may end in distinguishable crystals. 

 The outside of the stalactites is frequently covered with exceedingly mi- 

 nute crystals which, however, are so small and irregular that their forni 

 can only be determined in very few cases without a microscope. Some 

 microscopic groups of crystals obtained from the Ore No. 2 from Mina del 

 Diablo, most of them not over 1™™ in size, are composed of an aggregation 

 of apparently hexagonal plates of a bright hyacinth-red color with rounded 



