Investigation of Some Phosphatic Nodules from Dandaragan, 75 
Western Australia. 
No. 5— INVESTIGATION OF SOME PHOSPHATIC 
NODULES FROM DANDARAGAN, WESTERN 
AUSTRALIA.* 
by Keith R. Miles, D.Sc., F.G.S. 
Read, 9th May, 1944. 
INTRODUCTION. 
The work described in the following pages was carried out consequent 
upon field investigations of the various phosphatic deposits of the Dandaragan 
District, conducted by Mr. R. S. Matheson of the Geological Survey of Western 
Australia during the period May, 1941, to December, 1943. 
Specimens used in this investigation included a number of nodules recently 
collected by Mr. Matheson from pit CG on Cook’s Deposit (Upper Phosphate 
Bed)f located on Melbourne Loc. 704, and nodules (surface boulders) collected 
from the vicinity of pit BD on Minyulo Deposit (Upper Phosphate Bed) on 
Melbourne Loc. 284, Dandaragan. Several specimens of phosphatised wood 
collected by Mr. W. G. Campbell in 1906 from the South-East corner of Mel- 
bourne Loc. 957 about five miles north of the principal phosphate deposits 
on what is now' known as “ Summer Hill” Deposit (Lower Phosphate Bed), 
(site of the original find of phosphate rock in the Dandaragan District), were 
also sectioned and examined. 
THE NODULES. 
Description. 
Four nodules from the Cook’s Deposit were sectioned. They were 
marked A, B, C, and D respectively. It w'as seen that when broken 
they ranged from greyish yellow to brownish yellow in colour. The w T riter 
was informed by Mr. Matheson that unfortunately most of these nodules 
were darker in colour and were presumably slightly more ferruginous in 
composition than the average fresh nodules from Cook’s. 
The nodules from Minyulo Deposit, being surface boulders were rather 
weathered, and in places cellular, and coloured a dark brown except where 
whitened by adhering chalk. One fairly fresh dense and compact-looking 
specimen was sectioned and marked E. Several other specimens contained 
partly enclosed fragments of phosphatised wood. 
Mega . — On megascopic examination all nodules were found to consist 
essentially of detrital quartz grains cemented in a fine granular greyish to fawn 
coloured groundmass. The quartz grains vary in size from fragments up to 
5 mm. in diameter down to grains of microscopic size (<0*02 mm.). The 
average grain size of the quartz varies considerably in different specimens 
examined, e.g., nodule A contains a much higher proportion of comparatively 
large grains ( > 1 mm. diam.) than all other specimens and has an average 
grain size of about 0-37 mm. In nodules B, C, and D the quartz is more 
even in grain and has an average diameter of approximately 0-18 mm. 
Nodule E contains many large grains, though proportionally less than A, 
and has an average of about 0-26 mm. diameter. The grains range from 
sub-angular to rounded. 
* Published by permission of the Government Geologist of Western Australia. 
fSite of the recent find of Mesozoic reptile remains. See Teichert, C.. and Matheson, R. S. (6) 
L 8608/45 
