224 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



A specimen of copper ore from the dump of the Copper Age pros- 

 pect, selected as typical of the best ore. consists of coarsely crystalline 

 dark-gray carbonate which is brown where it has weathered on the 

 dump. This contains some interstitial blue-tarnishing chalcopyrite. 

 There is a coating of fine scaly chlorite on one side of the specimen. 

 The gray carbonate of this specimen, upon analysis, gave the following 

 results and ratios: 



Analysis of dolomite, Copper Age claim 

 [Earl V. Shannon, analyst] 



Constituent 



Manganese carbonate (MnCO 3) - - 



Iron carbonate (FeCO 3) 



Magnesium carbonate (MgCO 3)-- 

 Calcium (lime) carbonate (CaC03) 



Total 



Ratios 



B. 0058] 

 . 0875 }Q. 

 .3741) 



4674 



.5973 .5973 



The ratios between Mn + Fe + Mg to Ca = 47 to 60 or 1.00 to 1.27, 

 indicating some replacement of the essential magnesia of the dolomite 

 by lime. The ratio of iron plus manganese to magnesia is 1 to 4. 



The second analyzed dolomite came from the ore dump of the 

 Monitor mine, the specimen being one collected by Mr. J. T. Pardee 

 in 1910. It is mainly a coarse cleavable nearly white carbonate the 

 crystals of which are partly separated by pale-green films of a scaly 

 mica or chlorite. The carbonate contains some chalcopyrite. Upon 

 analysis this afforded the following results: 



Analysis of dolomite, Monitor mine 

 [Earl V. Shannon, analyst] 



Constituent 



Ratios 



Manganese carbonate (MnC03) 



Iron carbonate (FeCO 3) -- 



Magnesium carbonate (MgCO 3)-.- 

 Calcium (lime) carbonate (CaCO 3) 



Total. 



0. 00481 

 . 0713}0. 4848 

 . 4047) 

 .5917 .5917 



The ratio of the other bases to the lime is almost identical with 

 the last, namely 48 to 60, while the ratio of iron plus manganese to 

 magnesia is 1 to 5.32. 



A second specimen from the Monitor mine collected from the dump 

 by Mr. Calkins in 1912 is labeled Cl Carbonate and quartz." This 

 consists of a coarse rhombohedral carbonate with distinct cleavage 

 which is gray on fresh fracture and slightly yellow where lightly 

 weathered. Quartz in large rude prisms lightly coated individually 

 with a thin scaly green layer of chlorite penetrates the carbonate. 

 A little white calcite is associated with the gray carbonate as though 



