54 
State. An analysis made at the Geological Survey Laboratory of the purer 
portion gives the following results :— 
Magnesia (MgO) .. 
Lime (CaO) 
Carbon dioxide 
Moisture above 110° C 
Moisture at 110° C 
Iron and alumina 
Phosphorous pentoxide (P 2 0 5 ) 
Chlorine 
Sulphates 
Insoluble siliceous material 
The magnesia present is equivalent to about 99 per cent, of magnesium 
carbonate. 
[ 12 . 1 . 12 .] 
per cent. 
48-05 
0-07 
51-87 
016 
0-14 
nil 
trace 
nil 
0-26 
INFUSORIAL EARTH NEAR MICKLEHAM. 
By E. J. Bunn, F.G.S., late Director , Geological Survey. 
iVbout 7 miles due west from Donnybrook railway station, and 10 chains 
east from Deep Creek, on allotment 20, parish of Mickleham, a deposit 
of infusorial earth occurs that has been worked for a considerable time. It 
is on the north-west slope of a small outlier of basalt that the tunnels and 
shallow shafts have been driven and sunk. The deposit is being worked, and 
300 or more sacks of the material are stacked on the ground. The material 
is excellent, being quite white, very porous and light. Although there is 2 feet 
of this material, scarcely a trace of it is apparent at the outcrop. It thins out 
to 2 or 3 inches, and at the surface there is scarcely anything in the black soil 
to show that a bed exists. Probably along the course of the Saltwater and its 
branches there are numerous deposits, but trenching would be necessary in 
prospecting for them. 
They occur generally on 
a bed of clay below the 
basalt. Shallow lakelets 
have apparently formed 
on the clay, and the 
diatoms have accumu¬ 
lated until the shallow 
hollows have become 
filled with them. 
Infusorial earth of 
such good quality has a 
wide range of utility. 
The expansion of in¬ 
dustries is likely to lead 
to a greater consump- 
Fig. 22.—Section exposed in one of the shallow shafts. tion of this material. 
_ Scale, 16 feet to 1 inch. . There are already many 
known localities where infusorial earth exists, and systematic search would 
probably lead to the discovery of many others. 1 
[ 10 . 1 . 12 .] 
Diatomaceous Earth and its occurrence in Victoria, D. J. Mahony, Bull. Geol. Surv. Viet. No. 26. 
