Vol. 4] Lawson. — The Robinson Mining District. 



353 



calamine. With the quartz of the gangue are also chalcedony, 

 opal, fluorspar, and calcite. There are also some dendritic films 

 of manganese oxide. 



While in general the chief feature of the mineralization has 

 been the silicification of the limestone, there is abundant evi- 

 dence of minor fracturing and crustification and much of this 

 has occurred after the chief deposition of silica. 



From the general facts above set forth, it appears that in 

 the vicinity of the Ruth, without considering the mines farther 

 east, there are three well marked zones of metalliferous deposits, 

 viz. : — 



1. A central one containing sulphides of iron and copper in 

 the porphyry. 



2. A southern one carrying gold in the limestones below the 

 porphyry. 



3. A northern one carrying argentiferous galena with sub- 

 ordinate zinc and copper minerals in the limestones above the 

 porphyry. 



The segregation of the metals in this stratigraphic or struc- 

 tural relation to the porphyry is a most interesting fact but 

 with the limited data available it would be perhaps unwise to 

 attach too much significance to it. The fact is here recorded in 

 the hope that it may prove useful when considered in connection 

 with similar observations elsewhere in sufficient abundance to 

 lead to an inductive hypothesis. 



FAULTS. 



The general structure of the district, particularly as regards 

 the folding of the Palaeozoic strata, has been briefly described 

 in an earlier part of the paper. The essential features of the 

 structure are the Ruth syncline with an axis pitching northerly, 

 the rather flat Saxton anticline pitching southerly flanking this 

 on the west, and the broad spreading Rib Hill anticline, pitch- 

 ing to the southeast, flanking it on the west. These folds appear 

 to have been established before the advent of the earliest intru- 

 sive, the Weary Plat monzonite, which appears in the axis of 

 the Rib Hill anticline cutting across the folded strata. The sim- 

 plicity of these folds is interrupted by the more or less contin- 



