65 



THE PHOSPHATE MINERALS FROM ELDER ROCK. 



By D. Mawson, B.E., B.Sc, and W. T. Cooke, D.Sc. 



[Read November 6, 1906.] 



Plate XX., Fig. 2. 



Contents, 



section. page. 



I. Introduction ... ... ... ... ... ... 65 



II. Local Geological Featnres ... ... ... ... 65 



III. Elder Rock 06 



IV. Origin of the Epigenetic Fertilizer Contents ... 67 

 Y. Chemical Composition and Physical Characters 



of Faratooite ... .-. .•• ■•■ ••• 68 



VI. Summary ... ... ... ... ... ... "0 



I. Introduction. 



Elder Rock is situated ten miles south-east of Paratoo 

 Railway Siding, and, roughly, 160 miles north of Adelaide, 

 on the Broken Hill line. 



The occurrence of nitrogenous phosphatic rock from this 

 locality was announced by Mr. J. G. O. Tepper at the last 

 November meeting of this Society. Specimens of a red, 

 porous, ochreous rock, said to contain quantities of nitrogen, 

 ammonia, and phosphoric acid, were exhibited. 



Shortly afterwards several smaller occurrences were 

 reported, distributed at intervals in an east-north-easterly 

 direction from the original discovery. 



The "Elder Rock Nitrates Development Company" pro- 

 ceeded to exploit the deposit, but soon proved beyond doubt 

 its lim.ited nature, and ceased operations. 



II. Local Geological Features. 



The route from Paratoo Railway Siding lies across two 

 ranges of hills with flat land intervening. The first of these 

 is met one mile out, where the road follows a deeply eroded 

 creek-bed, cutting across the strike of the range, and expos- 

 ing strata of a familiar character. In conversation with Mr. 

 W. Howchin, who had already visited the locality, these 

 rocks were described as belonging to the middle division of 

 the South Australian Cambrian series; according to the 

 same authority they are described as "corresponding to the 

 Tapley's Hill slates and impure siliceous limestones and true 

 limestones of the Brio'hton series, with a general strike to the 



