♦BY W. H. TWELVETREES AND W. F. PETTERD. 3D' 



schist to con-espond Avith a lode fissure, and the lenticular 

 ore bodies with the ore shoots in a lode. The depths to^ 

 which these foliation planes extend depends (1) upon the 

 magnitude of the anticlinal or synclinal flexure to which 

 the sedimentary rocks were subjected, and (2) upon the 

 extent to which ihe secondary foliating agency aft'ected 

 them. This form of deposit has an advantage ovei* most 

 bodies, in that there has often been the opportunity for 

 the formation of numerous ore bodies on parallel lines 

 following parallel parting planes of the schist. The ore- 

 bodies come in and die out in these channels as ore coui-ses 

 do in a lode ; and there is in reality no more nor any less 

 reason for timidity or despondency in exploiting either,. 

 It will be noticed that on this supposition the ore was not 

 deposited in the beds before they were crushed and 

 foliated : consequently, by simple exclusion and without 

 further argument, the hypothesis that the metals were 

 precipitated on ancient lake bottoms Avhich have since 

 been raised and tilted, falls to the ground as far as the 

 Mount Read ore bodies are concerned. To gain some 

 knowledge of the true nature of the slates and schists,, 

 some of the unaltered slate (a dark greasy variety) from 

 Mount Read was powdered and treated in the test tube,, 

 first with a cold saturated solution of citric acid, then 

 heated, but no effervescence took place. Subsequent boil- 

 ing in HCl. gave the same result. The non-metalliferous 

 schist fi'om the same locality was subjected to the same 

 treatment. Some of this behaved in a similar manner ;. 

 but another piece gave signs of the p-esence of a carbonate^ 

 The microscopical test showed calcite. Slides of the schist 

 in the tunnels of the Hercules Mine sometimes show 

 abundant calcite, occasionally in a granular condition, as 

 if broken up by earth movements. That minor later- 

 movements have occurred is evidenced by the "greas^ 

 headings" in the mines. These are false walls, or parting 

 planes, where the rock has been shifted by earth stress^ 

 Under the microscope the powdered schist reveals its- 

 derivation from the slate very plainly. Both consist of 

 grains of alumina or aluminium silicate, with a little quartis^ 

 This schist is perhaps the most common on the HerctileS. 

 group of sections on Mount Read. It is hardly a tru^^ 

 schist, hardly even phyllite, which is a lustrous slate^ 

 Argillite, or argillaceous schist, would perhaps be the most 

 suitable name. There are, however, other descriptions on. 

 the range. There are clay slates, glossy with mica : these 

 are true phyllites. There are siliceous schists, which have 



