SUMMARY. 183 



main fissure, and although it has in many places the appearance of ore- 

 bearing ground has hitherto been found unproductive, all the ore having 

 been obtained from the wedge of limestone between the main fissure and 

 the quartzite. It is true that the prospecting done in the front limestone 

 has not been sufficient to pi'ove that it contains no ore bodies, but it has 

 been sufficient to discourage search in that direction. 



As far as prospected, the front limestone does not exhibit the crushed 

 condition that is so apparent in the wedge of limestone between the quartz- 

 ite and the main fissure. 



The quartzite in the Richmond. — The quartzite southeast of the Richmond shaft 

 appears to be a solid mass many hundred feet thick. Its contact with the 

 limestone is very irregular, and the rock near the surface is often displaced 

 to a greater or less extent by faults, but it is comparatively easy to explain 

 these irregularities and to account for the phenomena exhibited. Not so, 

 however, with the quartzite in the Richmond and Albion ground northwest 

 of the working shaft of the former mine. The quartzite in these two mines 

 consists of a narrow band from a few inches to 90 feet wide, which bends 

 and twists in many directions. It accompanies the secondary fissure which 

 leaves the face of the main body of quartzite somewhere near the Rich- 

 mond shaft. 



Formation of the narrow quartzite. — The manner in which the narrow band of 

 quartzite found its way into its present position seems to admit of but one solu- 

 tion, namely, that its occurrence is due to a fault or a succession of faulting 

 movements which followed the line of the accompanying fissure, and that 

 it originally formed part of the main body of quartzite, which must here 

 underlie the limestone. It is altogether improbable that it constituted a 

 distinct bed of quartzite laid down upon the back limestone. In this case 

 some indications of its existence would have been noticed in other parts of 

 Ruby Hill. It is not possible that it is quartz, and was deposited after the 

 formation of the fissure, as under the microscope it exhibits the structure of 

 quartzite. 



Back limestone. — The term " back limestone" is given to the limestone which 

 is found on the foot-wall side of the narrow band of quartzite. This rock 

 differs in many respects from the limestone which is encountered between 



