Pilbarite, a New Mineral from the Pilbara 
Goldfield. 
BY EDWARD S. SIMPSON, B.E., F.C.S. 
{Read Aug. 16, igio.) 
The mineral described in this paper has recently been found 
in small quantities above the water level in the main tantalite 
lode on Mineral Lease 86, at Wodgina, Pilbara Goldfield. The 
geology of this district and the nature of the tantalite lode have 
been dsecribed by our President in Bulletins 23 and 40 of the 
Geological Survey of Western Australia. The tantalite leases are 
pegged out on hilly country composed of greenstone schists, 
which are penetrated by numerous veins of pegmatite, these 
being at times sufficiently rich in tin and tantalum to constitute 
“ lodes.” The main tantalite lode is a strong pegmatite vein 
whose outcrop has been traced in a north and south diiection 
over a length of more than half a mile. Practically the whole 
tantalite yield of Wodgina has been obtained from this lode or 
from surface fragments weathered out of it. According to Mr. 
Maitland’s description, the chief constituents of this vein are 
albite and quartz. Some portions consist almost wholly of albite, 
others of quartz, whilst occasionally fine scaly lepidolite is a 
prominent mineral. Orthoclase, manganotantalite and cassi- 
terite have been recorded from it, and to this list must now be 
added Pilbarite. 
A few months ago a few fragments of a bright yellow ochreous 
mineral from this lode were sent to the author for determination. 
These were found to be strongly radio-active and to contain a 
considerable percentage of uranium and thorium. Such minerals 
being of considerable interest and value at the present time, a 
further supply was asked for, and in response to this request a 
sample of about two pounds in weight was received. A very 
full examination of this mineral has therefore been possible of 
accomplishment. 
The mineral is in nodules from the size of a pea up to that 
of a walnut. The largest piece weighs 30 grammes, the average 
size of fragment being about 5 grammes. The fragments are 
subangular in outline and in one or two instances portions of the 
surface suggest crystal faces. It is evident that this mineral is 
a hydrous pseudomorph after a probably anhydrous paient 
mineral. Examination under the microscope showed that it is 
amorphous and of a colloidal gelatinous or gummy texture. 
Such slight indications of cleavage and external crystalline form 
as are observed evidently owe their origin to the parent mineral 
and are not inherent characteristics of Pilbarite itself. 
