60 THE WEST AMEEIOAN SCIENTIST. 



CALIFORNIA DIAMONDS. 



For a period of more than thirty years the placer miners of California have oc- 

 casionally picked up small diamonds. The hydraulic washings at Cherokee, Butte 

 county, have bsen the most prolific. The diamonds are usua ly found by the min- 

 ers when cleaning up their sluices or while washing off the bedrock, though in some 

 few instances they have been picked up on the surface. As a general thing the 

 gravel in which they occur is mixed with lava, ashes, or other volcanic matter; zir- 

 con, platinum, iridium, magnetite, etc., being associated wi h the diamonds. While 

 many of these stones have been of goo I color, brilliant and perfect none weighing 

 over 3| carats have been found in th^ s ate. In size they have ranged usually from 

 about h ilf a carat down to stones of microscopic dimensions, the latter being numer- 

 ous in a few localities. So far as known $500 is the highest price for which any Cal- 

 ifornia diamond in the rough has been sold, though large numbers have found pur- 

 chasers at prices ranging from $10 to $50, and not a few at as much as $100. The 

 stones have been of all colors, white, yellow, straw, and rose, an 1 many of good wa- 

 ter. A few small diamonds have been found also in the placer diggings of Idaho, 

 being of about the same quality and occurring under the same conditions as in Cali- 

 fornia. In neither region have diamonds been made the object of special search, 

 those found having been picked up by miners while washing gravel for gold. Frag- 

 ments of diamonds have been noticed in the tailings from the quartz mills, being the 

 remains of stones which have been broken under the stamps. [ — C. G. Yale, in "Pre- 

 cious Stones." 



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CORUNDUM. 



This mineral has long been used in the arts as a preferable substitute for emery. 

 Its scarcity, and the expense of mining, has prevented its extensive use for the or- 

 dinary purposes to which emery is adapted by reason of its abundance. Corundum 

 is crude sapphire, and in hardness ranks highest of all minerals excepting the dia- 

 mond. Its use for grinding wheels is in great demmd, the superior quality of these 

 over emer^T- whee'.s having been demonstra' ed for nearly every purpose. It re- 

 quire s an extreme degree of heat to fuse the mineral, and grinding wheels made of 

 it are said to be subjected to fully 3,000 degrees, in the process of solidific ition. 

 This imparts a capacity of resistance to centrifugal force not attained in any process 

 of making up emery wheels, beside adding materially to the hardness of cutting 

 quality of the wheel. 



In some of the English collieries experiments have been made with ' water car- 

 tridges,' in which the gunpowder of the charge is completely surrounded by water. 

 It is stated that no flame followed the explosions, even when heavy blasts were 

 made. The water cartridge and ordinary gunpowder cartridges were fired in bags 

 of coal-dust, the dust being ignited by the latter, while the former simply dispersed 

 it in a dark cloud mixed with steam. The new cartridges are expected to render 

 great service in mines where fire-damp is present. 



