9^ 



were from a hard greenish-grey stone with conchoidal 

 fracture, emitting sparks under the chisel, dotted with black 

 spots (filled vesicles) from the size of a pin's head upwards. 

 The specific gravity was 2-8. The stone was obtained from 

 the Silver Queen Mine through Mr. W. F. Petterd, who 

 informs me that he is now quite satisfied that it is inter- 

 bedded with the slates. Mr. Alex. Montgomery, M.A., 

 Government G-eologist, has shown me looser descriptions, on© 

 of which looked like an agglomerate or brecciated tuff, but 

 my remarks will have reference to the compact variety. 



The slides prepared show a glassy ground mass devitrified 

 by globulites and felspar microliths, many of the latter with 

 curved, abortive, and ragged forms. A few of the larger 

 crystals show simple, rarely multiple twinning. The micro- 

 liths are crowded with inclusions which give them a corroded 

 appearance. The structure is what Eosenbuscli calls hyalo- 

 pilitic, a felted mass of felspar microliths with interstitial 

 glass. 



I have applied Levy's method of determining the nature 

 of the small felspars, viz., obtaining the extinction angle as 

 from the longitudinal axis of the microlith. I find this to go 

 as high as 30°, though quite a group collects round 24° and 

 26°. This indicates labradorite of average composition, the 

 most common type of felspars of the ground mass in basaltic 

 rocks. 



The most striking feature in the sections consists of 

 the numerous steam pores or cavities originally of gas 

 bubbles, irregular in size and shape, but often elon- 

 gated in the direction of flow, filled sometimes entirely 

 with a chloritic substance, sometimes with calcite or with 

 calcite bordered by chlorite, and sometimes containing 

 carbonate of iron and a little quartz. The calcite effervesces 

 on the application of acid and polarises brilliantly, contrast- 

 ing strongly with the border of feebly refracting chlorite. 

 This chloritic substance occurs as spherular aggregates filling 

 the vesicles. Where the section is sufficiently thick its colour 

 is a yellowish green, between crossed nicols it is steel blue 

 and shows faint interference crosses. The characters of 

 delessite approach those of the other chlorites so nearly as to 

 render its absolute determination difficult, but the indications 

 are those of this mineral, e.g., the colour is from colourless 

 to greenish yellow, according to the thickness of the slice ;, 

 the arrangement of the fibres is radial from the centre with 

 concentric interruption lines, through which they pass occa- 

 sionally without a break, and its occurrence in vesicles is 

 eminently characteristic of delessite. It is sometimes faintly 

 dichroic. "Where the section is thin the delessite filled vesicles 

 are thoroughly colourless, and single-refracting. Calcite 

 veins traverse the rock, presumably after consolidation. Thft 



