THE ORIGIN AND OCdIRUENCES OF l>HOSI>HATE 



|{0(1v AND THE PiiSSIBIEITY OF FlNDiNO 



PHOSPHATE DEPOSITS IN AUSTRALIA. 



By H. J. JENSEN, D.Sc. 



Read before the Boyal^Society of Queensland, 30^/i October, 1909. 



f'- Phosphoric Acid, which is an important plant food, is 

 constantly being extracted from the soil wherever intense 

 grazing or cultivation is practised. In our native scrubs, 

 where the plants and animals on dymg leave their remains 

 on the ground, most of the phosphoric acid is returned to 

 the soil, but when the beasts and plants of the held are 

 taken to the cities for consumption no such restitution of 

 phosphoric acid takes place ; and to prevent the land from 

 becoming absolutely exhausted the addition of mineral 

 fertilisers containing phosphate is essential. It is therefore 

 clear that from a nationa.1 and economic standpoint 

 prospecting for phosphoric acid is a more useful occupation 

 than hunting for gold. 



' SOURCE OF PHOSPHATE DEPOSITS. 



Most of the phosphate deposits of commercial value 

 throughout the world occur in sedimentary rocks, but 

 occasionally large bodies of mineral phosphate (Apatite) 

 are directly the product of igneous activity, p^s in Canada, 

 Norway, and Estremadura in Spain. 



Primarily all the phosphate of sedimentary rocks wa? 

 derived from igneous rock. All igneous rocks contain 

 phosphoric acid in small amounts, varying from .01 o 5.00 

 %. It occurs in the form of apatite .phosphate of lime wi\ fi 

 fluoride or chloride of lime), in small needles which crystallised 

 out in an early stage of the consolidation of the rock. As 

 apatite is generally one of the most soluble of the minerals 

 of igneous rocks, it readily passes into the soil, where it is 

 taken up by plants and into the animals which live on the 

 plants, or it passes into the rivers in solution and thence to 

 the sea, where it is tp.ken in by fishes, corals, molluscs, and 



