io6 
EDWARD S. SIMPSON, B.E., F.C.S. '. 
and lead, of which analyses are appended. 1 had the honour 
on a previous occasion* to describe to you the discovery 
and occurrence of pilbarite, a new ochreous mineral occurring 
in the outcrop of the lode. At that time it was recognised 
that pilbarite was a surface alteration product ot some as 
then unknown deep-seated mineral or minerals. I lie 
parent mineral, mackintoshite, and an intermediate product, 
thorogummite, have since been encountered at Wodgina,. 
and a full description of them is now in the press, f 
Briefly, the primary mineral, mackintoshite, is black, 
subvitreous and massive. It carries 35.60% UO a partly 
oxidised to U 0 3 by incipient development of the inter- 
mediate mineral, thorogummite. The latter is bright yellow, 
vitreous and massive. It carries 37.33% of TO, . The final 
product of weathering, pilbarite, is granular massive, bright 
yellow in colour, but with dull lustre. It carries 27.09% 
UO, . 
All three minerals contain radium in the following esti- 
mated proportions : — 
Mackintoshite, ir centigrams per ton. 
Thorogummite, 11 ,, ,, 
Pilbarite, 7 ,, 
Such quantities of radium might well be expected to more 
than pay for the cost of extraction, even though the latter 
is complicated by the presence of so much thoria, which in 
its turn would form, with uranium oxide, a valuable by- 
product. 
The composition of these minerals is as follow : — 
Uranium Minerals, Wodgina. 
uo. 
present 
37-33 
27.09 
UO 
none 
none 
Th 0 2 
24.72 
24.46 
31-34 
Cfi 2 0 3 
.10 
.12 
.19 
y 3 o, 
25 
•32 
•49 
Al 2 0 , 
trace 
trace 
■ ifi 
Fe 2 0 
trace 
.20 
FeO 
.20 
— 
— 
PbO 
7 - 9 ° 
7.78 
17.26 
CaO 
1.28 
1.62 
•57 
MgO 
.16 
.21 
MnO 
°7 
none 
none 
K 2 0 
— 
— 
.oq 
* See Jour. Nat. Hist. & Sci. Soc. of W.A., Vol. 3, No. 2, p. 13c 
t E. S. Simpson : “ Radium-uranium Ores from Wodgina, Geo 
Surv. W.A. Bull. 48. 
