PRINCIPAL PHOSPHATE DEPOSITS. 



29 



through the paste of the rock. The Caceres deposits are more 

 extensive, but the material is less rich in phosphoric acid. The 

 veins traverse a compact limestone regarded as Devonian, and 

 disperse themselves in the subjacent schists with thinning-out zones 

 in contact. Phosphate veins also occur in the Silurian schists, 

 which extend to the north of Alcantara, province of Caceres, of 

 Badajoz, Elvas, Zarza Mayor, Albala, Montanchez, Majadas, 

 Malpartida, Ceclavin, as far as Portalegre and Morvao in Portugal. 

 The size of the veins varies from 20 cm. (8 inches) to 8 metres (25 

 feet). The phosphate and the containing rock are of the same nature 

 as at Logrosan. The composition of Estremadura phosphate varies 

 very considerably, as the very complete analyses of Schucht repro- 

 duced here show. (See also p. 5.) 



TABLE XXL (a).— ANALYSES OF SAMPLES OF ESTRAMADURA 



PHOSPHATES. 



IX. North America. — There are four centres of phosphate 

 production in North America, viz. Canada, South Carolina, Florida, 

 Tennessee. In addition to these, deposits of less importance occur 

 in North Carolina, Pennsylvania, Massachusetts, Indiana, Kentucky, 

 and Alabama. 



Canada. — Deposits of apatite, crystallized in pockets and in 

 veins, are wrought in Canada. The pockets of apatite are met 

 with in beds of pyroxenit of variable magnitude but of great regu- 

 larity in stratified conformable layers in the gneiss. The paleozoic 

 limestones on which this gneiss lies are of the Laurentian age. The 

 gneiss is itself pierced by numerous crystals of apatite. Apatite is 



