GEOLOGICAL LABORATORY NOTES. 405 
been detected in the stone, although there can be little doubt that 
this oxidised lode-stuff has been derived from some form of pyrites. 
The gold is noted as occurring in three ways. 
1. In plates and patches spread out along the laminae of the 
slate, appearing bright and burnished-like in lustre, but in thick- 
ness hardly more than a mere film. 2. In specks and grains 
associated with quartz. 3. In grains and irregular masses enclosed 
completely in an aggregate of bismuth oxide and carbonate. 
The selenium is irregularly distributed through the stone. 
There is no character that I could recognise, to guide one in 
identifying the portions richest in this rare element. Heated in 
a closed glass tube most of the stone gives a black sublimate with 
the characteristic odour of volatilized selenium. When the 
portions of the stone richer in selenium are so treated, the subli- 
mate shows a red ring, inclining to crimson below the black. 
Any samples of the stone when rubbed briskly together emit the 
h 1 
char: istic di le smell suggestive of bisulphide of carbon. 
Oo 
The oxide and carbonate have evidently been derived from 
some mineral not now determinable. It is probable that the 
selenium and the bismuth existed as a selenide or a sulphide of 
bismuth. This sulphide or selinide of bismuth was probably 
auriferous, as in the case of the telluride of bismuth described by 
Professor David and Mr. Mingaye.! As work is progressing at 
the Mount Allen Mine we may hope for further information in 
regard to this occurrence of selenium. ' 
IL—Oy a Grapurric Stare From Yaucocrin, N.S. WALES. 
Graphitic slates crop out at a point about twelve miles north- 
west of Yalcogrin Station. They are interstratified with slates 
of Silurian age. These are again succeeded unconformably by 
Devonian Sandstones and quartzites. The lustrous and polished 
‘Appearance of the slate would lead one believe that it contained a 
high percentage of graphite. It marks paper readily when 
eae 
1 Records of the Geological Survey, N. S. Wales, Vol. 1. pp- 26,29: 
