CHAPTER II 



TABLE FOR THE DETERMINATION OF THE MORE COM- 

 MON MINERALS, BY THE USE OF THEIR PHYSICAL 

 PROPERTIES 



THIS table is arranged in two parts. Part I includes those 

 species which have a metallic luster and usually yield a streak 

 dark in color, and the mineral specimens are opaque, even on their 

 thin edges. Those with a bright luster are metallic and those with 

 a dull luster are considered as sub-metallic. 



Part II includes all those species which yield a streak, light in 

 color or colorless ; they are termed non-metallic. 



As the color of metallic minerals is quite characteristic and more 

 or less constant, Part I is further divided into divisions ; minerals 

 of nearly the same color and the species are arranged in each of 

 these divisions according to their hardness. 



In Part II, the non-metallic minerals (where the color of the 

 specimens may vary widely), the divisions are made according to 

 the color of their streaks, and those yielding streaks of nearly the 

 same color are placed in the same division; and here again the 

 species are arranged in the divisions according to their hardness. 



NOTE. AH material used for the tests should be homogeneous and when 

 crystalline the crystals should be used; remembering always that a mineral natu- 

 rally soft may appear harder than it really is from impurities, as sand or other hard 

 minerals. Hard minerals may often appear soft on the surface from chemical change 

 or weathering. Impurities often effect the color of the streak of non-metallic 

 minerals, yielding streaks darker than normal. 



The abbreviations used are. H. - hardness, C. - color, G. - specific gravity, 

 xls - crystals ; cleavage parallel to a crystal form is indicated by the letter repre- 

 senting that form, as cleavage m - cleavage parallel to the unit prism ; cleavage 

 r = parallel to the rhombohedron, etc. 



The common colors are placed first ; as, white, yellowish, or green would indicate 

 that the mineral is usually white, but yellowish specimens occur which are more 

 common than the green. The same principle applies to the order of other dfsrrip- 

 tivt- terms used. 



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