BY W. F. PETTERD. 67 
in columnar blades often a foot in length: it is usually white and 
glassy ; two miles east of the Parson’s Hood Mountain, of a 
grey colour, compact in structure, and a somewhat dull surface ; 
in the vicinity of Mount Pelion, in masses that are very pale in 
colour, almost white. 
228. TETRAHEDRITE (Fahklerz, Sulphide of Copper, Anti- 
mony, JC. 
This mineral is looked upon as a most important ore of Silver, 
not only because it is commonly rich in the desired metal, but also 
from the thoroughly established fact that it usually exists to great 
depth, so that its occurrence may, as a rule, be looked upon as 
predicting permanency in the metalliferous ore body in which it 
has been detected. It has long been the mainstay of the great 
mines of Saxony, where it has been worked for considerably over 
acentury. It often contains a considerable admixture of other 
metals, such as Zinc, Iron, Lead, or even Mercury may be present, 
and still more rarely, Cobalt or Bismuth. It has been discovered 
massive and richly argentiferous at Dundas as a lode formation 
which is reported to be of considerable size. A qualitative 
analysis of this mineral shows it to be a remarkably pure form of 
Fahlerz: it is practically a Sulphide of Copper, Antimony, and 
Silver, the latter metal often giving assay returns of over 250) ozs. 
per ton of mineral. In this mine it is found associated with 
Chalcopyrite. Occurs in limited quantity with Galena and various 
forms of Pyrites, Penguin Silver mine; found in the form of 
scattered blebs and narrow compact seams in a silicious matrix, 
with Sphleraite, Jamiesonite, Galena, and other minerals, Hay’s 
Prospecting Association, Castray River; it has also been reported 
to occur in several of the mines at Zeehan and Dundas; at Mount 
Lyell it is reported to occur in close association with cupriferous 
Pyrites; assays from this locality have given a return of above 
2400 ozs. of Silver and 1 oz. of Gold perton. The ore apparently 
occurs as amorphous lumps intermixed with the paler-coloured 
Pyrites. The manager 6f the Fahl Ore Silver Mining Company 
(Dundas) reports that “ A sample of 1 cwt. of ore from this mine 
which was forwarded to Germany has given the following returns :— 
Copper, 26 per cent.; Antimony, 15°45 per cent.; Arsenic, 1°5 
per cent. ; and Silver, 0°75 per cent. (equal to 245 ozs. per ton).” 
Ferriferous Tetrahedrite in decomposed Hornblende rock, Dundas. 
(Ballarat School of Mines Museum), 
229. THOMSONITE (Hydrated Silicate of Alumina and 
Calcium). 
A zeolitic mineral occurring in Basalt rock, Sheffield; in small 
vughs, but the identification is somewhat doubtful, as the samples 
are small and indistinct, occurring in clusters of microscopic 
