6 ' THE MICROSCOPE. Jan. 



On Identifying Minerals. 



By MELVILLE ATWOOD, 



SAN FRANCISCO, CAL. 

 [Report of a paper read before the San Francisco Microscoiiical Society.] 



The minerals which have been generally adopted as rep- 

 resenting the degree of hardness in minerals were sug- 

 gested and introduced by Mohs, and are as follows : Talc 

 1, rode salt 2, calc-spar 3, flnor-spar 4, apatite or wolf- 

 ram 5, feld-spar 6, quartz 7, topaz 8, sapphire 9, diamond 10. 



Many years ago the speaker had found considerable 

 difficulty in determining, with any degree of accuracy, the 

 hardness of minerals, the scale of hardness then in use, 

 and probably still at many colleges, being a small box con- 

 taining samples of the different minerals and a penknife. 

 The knife was seldom hard enough to scratch wolfram 

 representing 5 in the scale. To the prospector or miner 

 it is of the greatest importance to be able by some sim- 

 ple means to determine the degree of hardness. Many 

 fragments of corundum and quartz have been sent long 

 distances to have them determined, the sender thinking 

 them diamonds. 



It had been found, after many trials, that the easiest 

 mode of determining hardness was to have the minerals 

 representing the various degrees mounted something 

 like a writing diamond. For this purpose break the cor- 

 undum, topaz, etc., into small fragments, and after select- 

 ing those with fine, sharp points, proceed to mount them in 

 the following manner: Take a small rubber-tipped pencil 

 and extract the rubber from it. Then Avith a spirit lamp 

 melt some lapidary's cement into tlie vacant space ; with 

 a small pair of plyers take the fragments of minerals, 

 heat one end, and insert it into the cement. While the 

 cement is warm, by wetting your finger, you can mold it 

 into any shape you please ; and when cold, it will harden 

 and answer just as well as if set in metal, with the advan- 



