75 



at now. They had, however, developed kaolinization of the 

 silicates to an amazing extent, and the iron-constituent had been 

 <iompletely peroxidised to red haematite. The haematite was 

 everywhere finely disseminated throughout the kaolin. In the 

 contact-zones the haematite was hydrated to limonite, and a little 

 free silica in granular form, resembling quartzite, also occurred. 

 In depth pyrites were plentiful, and much of the free gold was 

 replaced by gold combined with tellurium. The porphyry-dyke 

 cited by the author appeared to be genuinely obtrusive, as it cut 

 off all the transverse veins it met. Kaolinization was greatly 

 advanced and had spread to the greenstone rock alongside. It is 

 between the dyke and the greenstone that a schistose structure 

 has been developed by pressure a ad shearing-strain, but the num- 

 ber of secondary minerals is surprisingly few • colloid silica and 

 limonite, forming the so-called " jasper " reefs, constitute the 

 lode veinstone proper, but its development is quite local. In 

 fact, the bulk of the paramorphism would seem to have been a 

 rapid passage of the greenstone to the stage of kaolin and chlor- 

 ite. A swelling of the rock in consequence developed the joint- 

 ings which now furnish the " soapy heads " of the author. 

 Where such a paucity of secondary minerals has been developed, 

 it is much more likely that they should aggregate into colonies 

 or kernels than that they should occur minutely disseminated. 

 To his mind the lusus naturce of the writer were but nodules 

 •of secondary origin, and principally of the class termed " spear" 

 pyrites, a variety which rapidly decomposes in contact with air 

 or rain-waters. Wad and pyrolusite also plentifully occur along 

 the graphito-pyritic belt. The pyrolusite is usually well crystal- 

 lised, and is at times associated with very rich ore. 



