228 Crystals of Argentiferous Galena. [April, 



veins and crystals can be demonstrated to have arisen from vapor 

 of the ore. 



A cavern was struck by the miners, at the depth of about twenty 

 feet, and the walls of this crevice were found to be covered with 

 crystals of argentiferous galena, associated with brown spar and 

 quartz. The crystal of argentiferous galena are in the forms of 

 octahedra, having their solid angles replaced by single planes, and 

 rhombic dodecahedra with their surfaces rounded and dimmed by 

 decrystallization, or by irregular deposits of minute particles of 

 the ore . There are also some cubic crystals which have their 

 surfaces much altered, and their angles effaced or blunted, and 

 which present depressions in the planes of the cube, as if the ore 

 had sunk, in a semi-fluid state, into a cavity. 



Some of the crystals exhibit the most decisive proof of their 

 ingenious origin, and have undergone a sort of eliquation, the in- 

 terior of its mass having flowed out, and left the exterior crust in 

 the form which the crystal originally assumed on cooling of its 

 surface. Some of these crystals are somewhat larger (hat a hen's 

 egg, and form very beautiful specimens to illustrate the origin of 

 the ore, and would ornament the cabinet of a mineralogist. 



We may suppose that the cavern in which the crystals occur, 

 was originally filled with molten galena, and that the ore ran 

 out from it into other crevices, and left the cooled and crystallized 

 ore on the walls; or that an open crevice allowed the vapor of 

 lead ore to sublime into the chamber, and that the crystals were 

 deposited on its surface by their cooling action. 



The appearance of the walls seem to indicate the latter theory 

 «s the most reasonable; for the crystals of lead ore were deposit- 

 ed upon the quartz and brown spar crystals, which do not appear 

 to have been bathed in the molten ore. I should assign the same 

 origin to the resplendent octahedral crystals of black cupriferous 

 blende, which are sprinkled over the surface of this cavern, and 

 to the crystals of copper pyrites which are associated with the 

 lead ore. — Boston Journal of JVatural History. 



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 opinions of the contributers to this journal. We prefer to give 

 the articles of our correspondents in their own words. It is then 

 optionable with us to state our opinions and views or not, or make 

 what we consider corrections. 



