MINERAL DEPOSITS OE FERTILIZERS 29 



a coastal belt containing both land and river phosphates. 

 The land phosphate is usually excavated, whilst the river 

 phosphates are often obtained by dredging. These phos- 

 phates are not so rich as those of some of the other deposits, 

 but can be concentrated up to 50 % or 60 % strength. 



African Phosphates. At Tunis and Algeria very large 

 deposits of phosphates occur, those produced near Gafsa 

 being somewhat soft, gravelly phosphates, containing 55 % 

 to 65 % calcium phosphate. In different parts of these two 

 countries, there are other rock phosphates which are harder 

 and more stony. Some of the larger lumps of these mineral 

 phosphates show a high content of calcium phosphate on the 

 outside, but contain an interior nucleus of calcium carbonate. 

 This fact suggests that these phosphates owe their origin to 

 an infiltration of soluble phosphate into calcareous rock. 

 At Safaga and Kosseir, on the Red Sea, and at Sebaia, on 

 the Nile, there are deposits which after concentration yield 

 products with from 60 % to 70 % phosphate of lime and 

 1 % t 3 % oxide of iron and alumina. 



South Africa contains low-grade deposits of phosphate 

 rock at Saldanha Bay, j ust north of Cape Town. Much of the 

 material is sent to the Transvaal where the need for phos- 

 phates is very great. It is estimated that 2000-3000 tons a 

 month will be turned out before long. In South West Africa 

 there are some smaller deposits at Cape Cross which are 

 now available. 



Table 6 has been taken from Ulman and Fritsch and 

 revised and added to for the purpose of this volume. It 

 gives a fairly complete list of the most important phosphatic 

 deposits, with some notes on their composition. 



