9 6 
EDWARD S. SIMPSON, B.E., F.C.S. : 
Thorium — This metal was discovered as long ago 
as 1828 by Berzelius, but was merely of scientific interest 
up till the invention of the incandescent mantle by 
Welsbach. This latter is composed almost entirely of 
thorium oxide, for which reason thorium minerals are in 
keen demand at the present day. In its metallic form, 
thorium has no applications. 
Thorium, like many other metals, is found chiefly in 
pegmatite offshoots from granite or syenite intrusions. It 
is found under a variety of circumstances, viz. : — 
(a) As the chief metallic constituent of a mineral, such 
as thorianite (oxide of thorium) and thorite (silicate of 
thorium). No such mineral is yet known in W.A. 
( b ) Forming with uranium the chief metal in a mineral 
such as thoriferous pitchblende, mackintoshite, thorogum- 
rnite, pilbarite, the last three of which occur in this State. 
(r) In small and inessential but often commercially 
important proportions in cerium and yttrium minerals, es- 
pecially monazite, w hich is the chief source of the industrial 
supply. Several such minerals are of local occurrence. 
The known sources of thorium in this State are : — 
Moolyella. — Monazite from this locality has yielded 
5.03, 5 - T 7 > 5- 2 4 and 5.02% Th 0 2 . See page 95. 
Cooglegong. — Monazite contains 3.80 and 4.38% 
ThO, . Fergusonite carries 1.02% Th 0 2 ; euxenite, 1.76%. 
Th 0 2 . See pages 13, 22. 
Wodgina. — Three minerals rich in thorium occur here, 
viz., Mackintoshite, 24.72% Th 0 2 ; Thorogummite, 24.46% 
Th 0 2 ; Pilbarite, 31.34% ThO, . For details see pages 
25, 26. 
Greenbushes. — Zircon sand carrying trace Th 0 2 . See 
P a g e 97- m . , , 
The other cerium minerals mentioned on page 95 also 
undoubtedly carry thorium, though no analysis of them is 
available. 
Zirconium — This is one of the least rare of the rare 
metals and one of the first to be discovered (Klaproth, 
1788). The oxide zirconia is stated by Clarke to form three 
parts in every ten thousand of the solid crust of the earth.* 
It is an important constituent of one very widely dis- 
tributed mineral, zircon, and of many much rarer 
minerals. It is not known in nature in the metallic 
state. Zircon is present in all igneous rocks, particularly 
in granites and syenites. Being very resistant to atmos- 
pheric attack, it "is detectable in most clays and sands 
and usually forms an appreciable percentageof titaniferous 
iron sands and other heavy sands. 
* F. W. Clarke : Data of Geochemistry. 
