101 
IMPRESSED PEBBLES. 
By E. J. Dunn , F.G.S., Director , Geological Survey. 
At Red Hill, about 2J miles from Stockdale, on the road from Strat¬ 
ford to Dargo, a tract of Devonian rock is crossed. In these rocks there 
are beds of conglomerate that range from a few inches to over 4 feet thick. 
The pebbles in the conglomerate consist of quartzite for the most part 
with here and there one of quartz. They range in size up to 3 or more 
inches long, and are pink, red, white, and brown in colour. 
The unusual feature about .the pebbles forming this conglomerate is that 
they are quite commonly impressed into one another, apparently through the 
exertion of enormous compressing forces. Many of the hollows that have 
resulted are up to an eighth of an inch in depth and several depressions 
are to be found on some pebbles. Why some pebbles were thus forced into 
others does not appear unless the pebbles varied in hardness and the softer 
pebbles had the others forced into them. A remarkable feature about the 
pebbles with depressions is that they have not apparently been deformed in 
any way. The edges of the depressions even are not raised as might have 
been expected, and the general contour of the pebbles appears not to have 
been disturbed. 
The hollows are not smooth but very uneven and rough. Sometimes 
the point of one kind of pebble remains imbedded in another. Probably 
when one pebble was invaded by another the action was extremely slow. 
Very beautiful examples are obtainable, and the hollows are in many cases 
unusually well marked. Similar occurrences have been met with by 
Professor Judd, F.R.S., and others in Scotland and on the (Continent, but 
none to excel these in the clearness and depth of the impressions. 
Quartz of secondary formation is to be seen in some of the hollows, so 
that it is possible that the hollows have resulted from a solvent action. 
Minute crystals of quartz are to be seen on the surface of some of the 
pebbles. 
[Report sent in 8.6.07.] 
THORIANITE. 
By E. ]. Dunn , F.G.S., Director, Geological Survey. 
Captain Collins, of the Commonwealth Offices, London, has sent a 
specimen of the new mineral, thorianite and draws attention to its great 
commercial value. It has brought as much as jQi,6oo per ton, but is now 
much lower in price. The great variations in the value of thoria are partly 
due to the trust which regulates market values. 
As monazite, another thoria-yielding mineral, occurs in Victoria, it is 
possible that thorianite may also be found. In appearance this mineral 
so exactly resembles in crystalline form and in colour the common limonite 
pseudomorph after pyrites that it might easily be overlooked. The specific 
gravity of thorianite is however nearly twice that of limonite. 
