S72 Professor Breithaupt on Osmelite and Cobalt Pyrites. 



white. Occurs massive. Primary form hexahedron. Its most 

 distinct cleavage hexahedral, — next in distinctness octahedral, 

 and the least perfect rhomboido-dodecahedral. Traces of con- 

 cretionary structure parallel with octahedral planes, intimate 

 that the octahedral figure is to be expected. Lustre shining 

 and metallic. Hardness equal that of glassy actynolite, or =z 7.25 

 — 7.75 (Breithaupt's scale). Specific gravity =r 6.74 — 6.84. 



On charcoal, before the blowpipe, it gives out copious arse- 

 nical fumes. Melted with borax, it affords a beautiful blue 

 glass. Arsenic and cobalt are thus shewn to enter into its com- 

 position. 



This new species of pyrites is distinguished from the axo- 

 tomous arsenical pyrites of Mohs, by inferior specific gravity 

 and crystallization-system ; from antimonial nickel-pyrites of 

 Breithaupt, by greater weight and greater hardness; from 

 cobalt-pyrites {Weissen Speiss-cobalt), by its more distinct hexa- 

 hedral cleavage and greater specific gravity. 



It occurs along with glance-cobalt, copper-pyrites, glassy acty- 

 nolite, precious serpentine, quartz, and sometimes cobalt-bloom. 



S. Miner alogical examination of' Russian Platina Sand. 



I was favoured by M. Schwetzau with a quantity of the Pla- 

 tina-sand, washed out of the sand of Nijnotaguilsk, in the go- 

 vernment of Perme, in Siberia. Of this Siberian sand there 

 are two kinds: the one is ferriferous, and contains platina; 

 the other, which is purer and more quartzy, afforded princi- 

 pally remarkably fine wash-gold. 



The platina-sand, even at first glance, appears composed of 

 grains of different kinds. I separated, by the eye, the follow- 

 ing minerals : 1. Platina. 2. Gold. S. Irid-osmine. 4. Silver- 

 white fiit grains. 5. Iseriiie, or magnetic iron-sand. 



The grains, from their appearance, could not have rolled 

 far, and must have been found at no great distance from the 

 place of their origin, for many of them are very sharp-edged, 

 or even bristled with points. 



1. Platina^ grains. — I attempted to separate these from the 

 iserine-grains, by means of the magnet, but was surprised to find 

 that not only the iserine, but also many of the platina-grains, 

 adhered to it. I found that some of the platina-grains were 



