themselves, as the minerals glauconite, magnetite, hematite, or limonite, 
and felspar, and not in any outside coating material. No calcium carbonate 
in crystalline form was recognised during microscopic examination of the 
nodules though it is possible that a little may be present as a decompo- 
sition product of the collophanite. A certain amount of calcium carbonate 
in the form of chalk is present as a coating on the nodules. 
A number of specimens of phosphatised wood (high grade phosphate) 
from Dandaragan were also examined microscopically. All specimens con- 
tained borer holes filled with lower grade phosphatic material similar in 
mineral composition to the phosphate nodules, i.e., containing inter alia a 
certain amount of iron oxide and alumina as glauconite, iron ore and felspar. 
The mineral composition and microstructure of the nodules point clearly 
to their inorganic origin and they are believed to have formed by precipitation 
of calcium phosphate about mineral grains in the original greensand. Phos- 
phatised wood fragments have often provided nuclei for the accretion of 
phosphatic material and the growth of nodules. 
ACKNOWLEDGMENTS. 
The writer wishes to acknowledge his indebtedness to Mr. F. G. Forman, 
Government Geologist of Western Australia for permission to publish this paper, 
and to Dr. R. T. Prider for assistance in revision of the text. The nodules 
A-E examined in the investigation have registered numbers 2 /2741A-D and 
2/2742 respectively and the phosphatised wood numbers 6979a-c in the Geo- 
logical Survey Rock Collection. 
REFERENCES. 
1. Lindgren, W. : “Mineral Deposits — The marine oolitic silicate ores,” p. 242, New 
York, 1913. 
2. Simpson, E. S. : “ Sources of Industrial Potash.” Geol. Surv. W.A. Bull. 77, 1919, p. 27. 
3. Dana, E. S. : Text-book of Mineralogy, 1932. 
4. Simpson, E. S. : “ Unusual types of petrifaction from Dandaragan.” Journ. Nat. 
Hist. & Sci. Soc. f W.A., Vol. IV., 1912, pp. 33-37. 
5. Campbell, W. D. : Geol. Surv. W.A Bull. 26, Misc. Rept. No. 3, 1907, pp. 14-20. 
6. Teichert, C, and Matheson, R. S. : “ Upper Cretaceous Ichthyosaurian and Plesio- 
saurian Remains from Western Australia.” Aust. Journ. Sci. Vol. VI, No. 6, 1944, 
pp. 167-170. 
7. Matheson, R. S. : “ The Phosphate Deposits in the Dandaragan District, S.W.” 
Unpublished. 
