BY EDWD. B. LINDON, A.R.S.M. 63 
IX.—OXIDES OF SILICON. 
Quartz—Comp. Si O,. 
This is a mineral of most widely-spread occurrence, whether as 
a rock-forming constituent or in the form of veins traversing such 
rocks. It is not my purpose to give a long list of places in which 
quartz occurs, but only such cases in which some particular kind 
or form is found. It is also unnecessary to mention all the 
minerals which occur with quartz for their matrix. 
Very few endormorphs in quartz crystals have yet come under 
my notice, cassiterite from Stanthorpe, gold from some few 
localities, copper pyrites from Marengo goldfield, and calespar 
and pyrites from Gympie, being all I have noticed in Queensland 
Prase has been found in the neighbourhood of a diorite dyke 
in the Cape River district, and at Stanthorpe. 
Agates are found in large quantities at Agate Creek, Etheridge ; 
in the Burnett district ; and at Mackay. 
Jasper occurs at the Diamantina in the Burnett district, and at 
Rockhampton. 
Chalcedony is largely found about Springsure, also at Mackay 
and many other places. Mr. R. L. Jack, in his report on the 
Hodgkinson goldfield, writes as follows :— 
“The nearly parallel valleys of Caledonian Creek (Glen Mowbray) and 
the Hodgkinson River are bounded on the right or north-eastern side by 
the Mount McGann Range, and on the opposite side by the Mount Robert 
Range. These ranges have had their trend determined indirectly by the 
forces which compressed the strata of the district from south-west to north- 
east, and threw them into long folds from south-east to north-west. After 
the strata had been compressed into nearly as small a compass as they 
would go into—i.e., till they became nearly vertical—the further operation 
of the same pressure resulted in the formation of fissures along lines of 
weakness; which lines of weakness were found in the bedding planes 
dividing the upturned strata from one another. These fissures, which are 
nearly, but not exactly, parallel with the outcrops of the strata, have been 
filled with a rock of great hardness, which, by its power of resisting 
denudation. has given rise to the Mount McGann and Mount Ronert 
Ranges. Both of these ranges occur in zones, in which the hard rocks in 
question are clearly grouped together, while the intervening softer ‘country’ 
has been channelled by the Hodgkinson River and Caledonian Creek into 
deep valleys. 
““The material with -vhich the fissures are filled forms veins and dykes, 
from 3 to 40 feet in width, of pure silica in almost all its various forms. 
It frequently resembles quartzite, and occasionally passes in ribbon jasper 
and chalcedony. The veins are often so laminated parallel to their sides as 
suggest that they may be beds rather than veins; but the modes in which 
they now and then cut across the adjacent strata, although preserving a 
