BY. EDWD. B LINDON, A.RS.M. 39 
Referring to Gympie, Mr. A. C. Gregory says, “ the Devonian 
slates* in Queensland, where composed chiefly of silica, with little 
alumina, seldom contain metalliferous veins cf any importance, 
and it is only where lime or magnesia is combined in considerable 
quantity that the quartz veins which traverse them present any 
notable mineral deposits; and it seems that the presence of the 
alkaline earths forms conditions which are specially favourable to 
the deposition of metals. The rocks in which the productive 
gold reefs at Gympie are worked belong to the series which 
contains a large proportion of lime; while the slates which dip 
below them from the N.E. are nearly devoid of lime and magnesia, 
and have not shewn indications on the surface of any valuable 
mineral deposits ; and it may be expected that, on penetrating 
through the calcareous rock, the reef will cease to be productive 
as they enter the siliceous slates beneath. The quartz and 
calcspar of the veins contain much iron pyrites, which also 
abounds in the side rock near the quartz veins ; and although the 
gold is generally mixed with the pyrites, yet far the larger pro- 
portion is in separate and distinct pieces, and there is a tendency 
to form separate groups; but the manner in which the crystals of 
quartz, calcspar, and pyrites cut one another, and are indented by 
the gold which is in other parts moulded to the angles of the 
crysials, shows that they were all deposited at the same period, 
while the lime taking the form of calcspar indicates that the 
deposition was at a low temperature.” Galena also is not un- 
frequently found accompanying gold in the calcite and quartz 
formation, and the gold also sometimes appears on the faces of 
“slickensides” on an impure graphite. 
At the junction of Didcot and Chowey Creeks, near Mary- 
borough, Mr. Rands says that gold in considerable quantities and 
sometimes beautifully crystallized is found in the Mount Shamrock 
P.C. in (1) a breccia, consisting of angular fragments of fine 
grained aluminous and siliceous rocks cemented together with a 
hard cement of oxide of iron and silica, throughout which are 
numerous quartz blebs; (2) a yellow ochre, containing a fair 
percentage of oxide of bismuth; (3) a brown iron ochre with 
veins of glassy quartz running through it and bunches of oxide of 
bismuth; (4) earthy hematite with siliceous veins and quartz 
blebs. The gold seems to be specially associated with the 
bismuth, for the veins of oxide of bismuth are exceptionally rich ; 
* These Gympie slates are now referred to the upper carboniferous series 
by Etheridge. 
