38 CATALOGUE OF MINERALS ; 
Reef and from microscopic examination its proximate composition 
would appear to be, quartz ro per cent., trinclinic felspar 80 per 
cent., and decomposed pyritous element 10 per cent. Mr. 
D’Oyley Aplin mentions a case at Ban Ban in the Gayndah 
district, where ‘‘ there is no appearance of any mineral lode or vein 
of any kind on the spot. The material, of which three tons were 
sent to the Sydney Mint for assay, and which resulted in a return 
of 1 oz. 6 dwts. of gold per ton, was taken from a mass of partially 
decomposed felspar porphyry, probably a dyke, but exhibiting no 
traceable outcrop. It is in a loose rubbly condition, and is 
exposed in a somewhat abrupt face on one side of a broad gully 
running into Sandy Creek, a tributary of Barambah Creek. 
Infiltrations of green and blue carbonates of copper form thin 
filmy coatings to the numerous surfaces produced by the dis- 
integration of the rock, and oxide of iron now fills the cavities 
once occupied by crystals of pyrites. Both the copper and the 
gold have doubtless been derived from the decomposition of 
auriferous sulphides, which appear to have been developed 
sporadically through the mass, and not collected into veins.” 
On the relation of intrusive trap-rocks to the auriferous vein- 
stones, Daintree further remarks ‘that in nearly all veins due to 
this apparent cause calcspar and pyrites are largely represented, 
none of them being composed entirely of pyrites. All veinstones 
of this class are decomposed by acids, and are rarely composed 
of quartz alone. The associated gold is a/ways alloyed with a 
large percentage of silver, and assumes also much of the character 
of the latter metal in its native state, being filiform and dendritic. 
It often takes a thread-like structure, which is technically known 
among Queensland diggers as ‘‘spider-leg” gold. The analysis 
of the ‘ spider-leg” metal from the Upper Cape diggings by Mr. 
R. Smith, of the Metallurgical Laboratory, Royal School of Mines, 
London, gave :— 
Gold. E : : : . 89.920 
Silver . : ; : : : 9.688 
Copper ‘ : : : : 0.128 
Lead . ‘ : , é 0.026 
Bismuth ‘ : ‘ ‘ ; none 
Iron : - : ; 3 0.070 
99.832 
Micaceous and hornblendic schists, a rather novel matrix for 
gold, from Mount Davenport, Lower Cape River, are found to be 
auriferous ; also steatitic schists from the Upper Cape River are 
found to carry nearly 2 dwts. of gold per ton. 
