ASSAYING. 



135 



.-SAMPLES TAKEN 30 FEET APART, BEGINNING AT THE END OF THE FIRST CROSS-CUT IN 

 THE "FRONT" LIMESTONE ON THE SIXTH LEVEL OF THE K. K. 



No. 



Description. 



Assay value 

 in silver. 



This limestone was of a grayish-white color, sometimes 

 ■ friable and sometimes compact. It did not differ from 

 the ordinary limestone. 



Cent!. 



Trace. 

 Trace. 



From contact with main Assure 



Determination of carbon in various Hmc S tones._The determinations were made in the 

 following manner: One hundred grains of finely pulverized rock were dis- 

 solved in hot chlorhydric acid, filtered, and the residue was dried at above 

 100° and weighed. This insoluble part was ignited and the carbon deter- 

 mined by difference. 



Description. 



Black limestone at contact with quartzite on the oross- 

 cut from shaft 1,200-foot level of the Kiohmond. In- 

 soluble matter 6.5 per cent 



"Back " limestone at end of cross-cut on the seventh level 

 of the Richmond. Insoluble matter 7.24 per cent 



Per cent, of 

 carbon. 



1.50 

 0.84 



A great deal of the limestone between the main and secondary fissures 

 carries free carbon, the amount sometimes reaching 1 per cent. 



An examination was made of the clay from the main fissure from all 

 the points where it is exposed in the Eureka mine, for the purpose of deter- 

 mining the quantity of the carbonates of lime, etc., which it contained. 

 The largest percentage of carbonates obtained was 85 per cent, and the 

 lowest 15 per cent. As a rule the clay was most calcareous near the sur- 

 face and the most silicious below, though there were local exceptions. As 

 it was in part the product of attrition and decomposition of walls of quartz- 

 ite, limestone, and shale, and no doubt in part also a product of the decom- 

 position of rhyolite, its variable composition is accounted for. 



