104 DEPOSITS OF PHOSPHATE OF LIME. [bull. 46. 
are about 25 to 30 per cent, of grains of carbonate of lime, and 70 to 75 
per cent, of phosphatic pebbles. The phosphate grains are equally 
plentiful all through the upper 10 feet of the bed, but below this they 
begin to grow scarcer and scarcer, until the bed gradually runs into the 
White Chalk (Oraie Blanche). In this lower bed no phosphatic nodules 
are found, but in their place there occur beds of brown, siliceous nodules 
lying between the strata. The overlying phosphate bed (Craie Grise 
or Oraie Brune) is a regularly stratified deposit and dips gently to the 
northwest. 
The phosphate grains were at first thought to be glauconite which 
had been turned brown by weathering. They are of a brown color and 
are very porous. When exposed to the action of heat for some time 
they become crumbly and very easy to grind. This is explained by Mr. 
JSTivoit 1 as being caused by the decomposition of the animal matter in 
the nodules. The specific gravity is 1.80 to 2.90. The phosphatic bed 
runs in a band of several hundred meters' breadth, through Cuesmes, 
Hyon, Ciply, Mesvin, Nouvelles, and Spiennes, all in the province of 
Eainaut. Estimating the surface of the belt as 180 hectares (444.78 
acres), and supposing that mining can be carried on to a depth of 8 
meters, there would be 14,500,000 cubic meters of workable rock in the 
place. 2 
The upper part of the phosphate bed averages 11.50 per cent, of phos- 
phoric acid (see analyses p. 107). A large part (50 to 55 per cent.) is 
composed of carbonate of lime. Numerous methods have been tried to 
separate the phosphate from the matrix. Treating the mass with hydro- 
chloric acid 3 has been tried, in the hope of dissolving out the carbonate 
and leaving the phosphate untouched, but it was found that the acid 
attacked the phosphate at the same time as it did the carbonate. An- 
other method is to expose the mass of nodules and matrix to the air for 
some time in order to allow it to disintegrate. It is then separated from 
a part of the associated carbonate of lime by shaking on a screen, or 
washing in a stream of running water, which carries off the more finely 
divided part of the carbonate. Sometimes the rock is ground, and a 
considerable part of the limestone removed by a fan. This method is, 
however, not as efficient as the washing process, and is only used 
where-water is scarce. By none of these processes has the quality risen 
above 40 to 50 per cent, phosphate of lime. 4 
An examination of the analyses given will show that the freer the 
phosphatic grains are from the calcareous matrix, the nearer they ap- 
proach in composition to the nodules of the Ciply Conglomerate. 5 They 
1 Mr. Nivoit: Comptes rendus Acad, sci., Paris, vol. 79, 1874. 
2 Cornet and Briart: Bull. Acad. roy. Belgique, 2d series, vol.37, 1874, p. 841. 
8 A. Petermanu : Bull. Acad. Sci. Roy. Belgique, vol. 39, 1875, p. 31. 
4 According to Cornet experiments are now in progress which indicate that the pro- 
portion of phosphate may be raised to 65 per cent. See Quart. Jour. Geol. Soc. 
London, vol. 42, 1886, p. 334.— N. S. S. 
6 Mr. Nivoit: Compt, Rendus Acad, sci., vol. 79, Paris, 1874. 
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