Geology and Mineralogy. 81 



Careful examinations of the accessible portions of the Schuyler 

 mine have never resulted in the discovery of thread silver. 

 Metallic copper was found, however, in the Passaic mine in the 

 same vicinity. 



Laboratory. 112 Water St., New York City. 



15. On the Vanadates and Iodyrite from Lake Valley, Sierra 

 County, New Mexico ; by F. A. Genth and G. vom Rath. — This 

 interesting paper contains descriptions of vanadinite from the 

 Sierra Bella and Sierra Grande mines, of endlichite, a vanadife- 

 rous mimetite, and of fine crystals of descloizite. The mineral 

 called endlichite, after Dr. F. M. Endlich, superintendent of the 

 Sierra Mines, is a sub-species intermediate between vanadinite and 

 minetite. It occurs in crystalline groups with columnar structure 

 sometimes radiating, also sheaf-like ; the hexagonal form, charac- 

 teristic of the group, is frequently distinct. The color varies from 

 white to yellowish white or straw-yellow. The two analyses by 

 Dr. Genth, proved that the vanadium and arsenic were present in 

 the ratio of 1:1. One of these gave, after deducting impurities, 

 and recalculating to 100: 



As 2 5 V 2 6 CI PbO 



10-73 1-94 2-18 79-15=l00-0O 



The crystals of descloizite are exceptionally fine for the species. 

 They include minute crystals mostly of a red to reddish-brown 

 color, generally united in groups or forming incrustations ; also a 

 larger variety up to 8 nira in diameter and brownish-black to black 

 in color. The former are octahedral, the latter rather prismatic 

 in habit. Careful measurements by vom Rath go to prove that 

 the species is orthorhombic in form, not monoclinic as made out by 

 Websky. Several analyses of the different varieties conform to 

 the generally accepted formula for the species, analogous to those 

 of adamite, libethenite and olivenite. Iodyrite also occurs with 

 the vanadates at the Sierra Grande mine in sulphur-yellow hexag- 

 onal crystals, or in crystalline masses. — Amer. Philosoph. Soc, 

 April 17, 1885. 



16. Hardness of the Diamond. — At a recent meeting of the 

 New York Academy of Sciences, Mr. G. F. Kunz called attention 

 to some experiments made by the Messrs. Tiffany upon a diamond 

 of extreme hardness. In the rough state it had a rounded form 

 and was of composite crystallization (" round bort "). 



It had been cut into the rude outline form of a brilliant, and its 

 table had been placed on a diamond polishing wheel for 100 days. 

 The average circumference of that part of the wheel on which 

 it was placed being about 2-|- feet, and the wheel going at the rate 

 of 2,800 revolutions per minute, the surface that traveled over the 

 diamond table amounted to over 75,000 miles. At times, four 

 and eight pounds were added to the usual 2^ to 2\ pounds of the 

 clamp or holder, and for a time forty pounds extra were added, 

 this last causing the wheel to throw out scintillations for several 



Am. Jour. Sci. — Third Series, Vol. XXX, No. 175, July, 1885, 

 5a 



