THK NONMETALLIC MINERALS. 37 1 



North (ii>riimiiy occupy an irregular area bounded on the northeast by 

 the town of Weilburg, on the northwest by the Westerwald, on the 

 east by the Tauiui.s Mountains, and on the south by the town of Dietz. 

 The pliosphorite occui's in the form of irregular nodular masses of all 

 sizes up to masses of several tons weight, embedded in chi}' which 

 rests upon Devonian limestone and is overlaid ))y another stratum of 

 clav- The phosphate-bearing clay varies in thickness from 6 inches to 

 10 feet. With the phosphate nodules are not infrequently associated 

 deposits of manganese and hematite. Davies regards the deposits as 

 of early Tertiary age. The color of the freshly mined material varies 

 from pale buff to dark brown, varying in specific gravity from 1.9 to 

 2.8, the quality deteriorating with the increase in gravity. Selected 

 samples of the staple nodules yielded as high as 92 per cent phosphate 

 of lime; but the average is much lower, being but about 50 to 60 per 

 cent phosphate of lime. (Specimens Nos. 66827, 66828, U.S.N.M., 

 from Gleisenberg and Heckholzhausen.) 



Belgium. — Nodular phosphates belonging to the Upper Cretaceous 

 formations occur in the province of Hainaut, where they form the 

 basis of an extensive industry'. The nodules, which are generally of 

 a brown color and vary in size from the fraction of 1 to 4 or 5 inches 

 in diameter, lie in a coarse-grained, friable rock called the brown or 

 gray chalk, which itself immediately underlies what is known as the 

 Ciplej^ conglomerate. The phosphate-bearing bed is sometimes nearly 

 100 feet in thickness, but is richest in the upper 10 feet, where it is 

 estimated the phosphatic pebbles constitute some 75 per cent of its 

 bulk. Below this the bed grows gradually poorer, passing by grada- 

 tions into the white chalk below. 



The overlying conglomerate also carries phosphate nodules, which 

 carry from 25 to 50 per cent phosphate of lime. Owing to the hard- 

 ness of the inclosing rock they are less rained than those in the beds 

 beneath. The mining of phosphates is carried on extensively near the 

 town of Mons, on the lands of the communes of Cuesmes, Cipl}^, Mes- 

 vin, Nouvelles, Spiennes, St. Symphorien, and Hyon. The annual 

 output has gradually increased from between 8,000 and 4,000 tons in 

 1887 to 85,000 tons in 1891. Other phosphatic deposits are described^ 

 as occurring in the provinces of Antwerp and Liege. 



SjMin. — Important deposits of phosphorites occur between Logrosan 

 and Caceres, in Estremadura Province. The deposits are in the form 

 of pockets and veins in slates and schists supposed to be of Silurian 

 age; at times a vein is found at the line of contact between the slate 

 and granite. The veins vary in thickness from 1 to several feet, the 

 largest being some 20 feet and extending for over 2 miles. This is by 



^ Annales de la Societe Geologique de Belgique, XVII, 1890, p. 185. 



