THE NONMETALLIC MINERALS. 377 



Experimental shafts sunk to a depth of 250 feet have failed to bring to 

 light any deeper lying beds. 



Analysis of gray Navassa phosphate. 



Water, at 100 C 2.33 4 



Organic matter and water of combination. 7. 63 



Lime 34. 22 



Magnesia .51 



Sesquioxide of iron and alumina 15. 77 



Potash and soda 86 



Phosphoric acid 31.34 



Sulphuric acid 28 



Chlorine .15 



Carbonic acid 1.84 



Silica 4.53 



Bone phosphate 68. 46 



Bone phosphate (dry basis) 70. 09 



Analysis of red Navassa phosphate. 



Loss on ignition 14. 223 



Lime 23. 090 



Magnesia Trace. 



Sesquioxide of iron 9. 796 



Alumina 18. 425 



Phosphoric acid 29. 779 



Sulphuric acid 1. 160 



Carbonic acid (by difference) 3. 527 



Bone phosphate 65. 037 



Specimens Nos. 10247, 73245-73248, U.S.N.M., show the variable 

 character of the phosphate rock, and Nos. 73242, 73243, U.S.N.M., the 

 associated coral work. 



The Aruba phosphate is described as a hard, massive variety of a 

 white to dark-brown color. The underlying corals of this island are 

 sometimes found phosphatized. An analysis given by Davies 1 is as 

 follows: 



Per cent. 



Moisture 8. 50 



Water of combination 4. 15 



Phosphoric acid 2 28. 47 



Lime 34. 07 



Magnesia 45 



Carbonic acid 3 2. 30 



Oxide of iron 4. 49 



Alumina 9. 48 



Sulphuric acid 1. 81 



Insoluble siliceous matter ... 6. 28 



100. 00 



a D. C. Davies, Earthy and Other Minerals, p. 177. 



2 Equal to tribasic phosphate of lime, 62.15 per cent. 



3 Equal to carbonate of lime, 5.22 per cent. 



