442 Transactions. 



blende is rarely present. The rock seems to be most closelv 

 related to the phonolites and tinguaites, the soda amphibole 

 talcing the place of the segerine common to those rocks, and 

 nepheline not being represented. The acid nature of the feld- 

 spar prevents its inclusion with the diabases or Hohenbegger's 

 teschenites, to which it has some affinities. 



Its occurrence is only another example of the numerous 

 varieties in which the crystallization of the magma beneath 

 has resulted, and the determination of the respective formation 

 of tegerine, soda amphibole, or nepheline is doubtless to be 

 sought in the varying chemical composition due to magmatic 

 differentiation. 



The Occurrence of Gold. 



An examination of the valley containing the mine leads to 

 no sign of the auriferous rock on the surface, and no sign of 

 pyrites or other possible gold-bearing minerals in the streams. 

 A drive indicated on the map pierces the solid bostonite on the 

 upper side of the valley. Two shafts are sunk lower down, 

 about 15 ft. above the level of the stream-bed. The only one 

 accessible was in a fair state of preservation, but, owing to 

 water, could only be descended a distance of 20 ft., to the first 

 cross-drive. 



The following materials wall the shaft and the drive : 

 (1) About 11 ft. of loam derived from decomposition of the 

 bostonite, and from vegetable sources ; (2) about 1 ft. of very 

 decomposed bostonite ; (3) cap of decomposed syenite ; (4) solid 

 syenite ; (5) the last 18 ft. of the drive is walled with friable mi- 

 caceous sandstone. (See Plate XIII, section AA, through drive.) 



Along the border-line of the decomposed bostonite was to 

 be seen a band about 3 in. in thickness of hard undecomposed 

 mineralised bostonite, mention of which is made under " Petro- 

 graphy." The syenite is in almost every specimen obtained 

 pyrites-bearing, and the mineralised bostonite is very rich in 

 that mineral. 



Assays of the samples obtained gave results as follows : — 



No. 1. — Syenite showing in hand - specimens no visible 

 pyrites (mean of three assays) : Gold = 0-000066 per cent., 

 silver = 0-00033 per cent. ; giving, per ton of 2,240 lb. — gold = 

 10-45 gr., silver = 2 dwt. 1*74 gr. 



No. 2. — Sample showing a few small specks of pyrites on 

 fractured surface (mean of three assays) : Gold = 0-00021 per 

 cent., silver = 0-00099 per cent. ; giving, per ton — gold = 1 dwt. 

 8-92 gr., silver = 6 dwt. 12-8 gr. 



No. 3.— Sample showing plentifully specks and small flakes 

 of pyrites on fractured surface, the richest sample in pyrites 

 obtainable (mean of three assays) : Gold = 0-0013 per cent., 



