Another Upper Greensand coprolite is raised in the neighbourhood of Boulogne, and sent over to this country, for use with higher class phosphates. It occurs in large grey nodules, with frequent organic, debris, and is widely distributed along the north-eastern coast of France, from Havre to the Flemish border. Though poor in phosphoric acid, its impurities are principally non deleterious, and therefore its phosphate is more easily available. Analyses by Voelcker of 5 samples of Boulogne coprolites gave respectively :—Tribasic phosphate of lime : 46.43, 46.43, 45.19, 38.61 per cent. ; carbonate of lime : 8.07, 11.93, 10.27, 8• 95, ; fluorine (3 samples): 2.08, ; oxide of 'iron : 2.89, 3.54, 6.24, 3.52 ; alumina : 3.09, 3.66, 3.64, 5.39, 4.94 ; insoluble siliceous matters : 24 .93, 28.45. France possesses two other important deposits of coprolites, known as the Ardennes and the Bellegarde beds. The former are of greater importance than the Boulogne coprolites, and are largely and successfully used in French agriculture, as a simple finely-ground powder. The annual production of these beds was estimated at 25,000 tons in 1872, and has very materially increased since. The Bellegarde coprolites may possibly exercise some local influence, but the low proportion of phosphoric acid in the material will prevent its wider application.
Coprolites are also said to be abundant in Germany, and to occur sparsely in Canada. Russian coprolites are, perhaps, rather better known, but they are of very poor character, giving :—Tribasic phosphate of lime, 33-48 per cent.; carbonate of lime, 5i; fluoride of lime, 3i; iron and alumina, 6; insoluble matters, 304-43.
Apatite.—Apatite is a definite crystalline mineral, and is the purest phosphate met with in an inorganic state. There are two varieties, known as " fluor-apatite" and " chlor-apatite," according as the lime not existing as phosphate is combined with fluorine or chlorine. Sometimes both forms are present. These minerals are found in veins, in primitive formations and volcanic rocks, princi pally in Scandinavia and Canada, but also in Bavaria, Bohemia, Saxony, and Switzerland, as well as in New York and New Jersey, in America. As they contain from 75 to over 90 per cent. of tribasic calcium phosphate, they are a valuable source of phosphoric acid, but a well-conditioned superphos phate can hardly be made from them alone. They answer admirably, however, in conjunction with phosphates containing less phosphoric acid and more carbonate of lime. They are very hard, and of vitreous appearance, with a colour varying from yellowish to greenish-white.
The vein of chlor-apatite, which was discovered some years since on the southern coast of Norway, has been worked on a considerable scale by the Bamble Phosphate Co., and others. The expense of preparing the rock for market by hand-trimming is great. The present annual production barely reaches a few thousand tons ; while the extent of the deposit was estimated at 75,000 tons. Some times the mineral yields as muoh as 90 per cent. of phosphoric acid in bulk, but generally it does not exceed about 75 per cent. It consists essentially of :—Tribasic phosphate of lime, 75-901 cent. ; chloride of lime, 11-41; iron and alumina, 2-3 ; siliceous matters, 14-11/. Some samples
also contain about 11 per cent. of fluoride of calcium.
The Canadian variety is imported to a greater extent than the foregoing. It is a fluor-apatite, sometimes containing also carbonate of lime, which is said never to be the case with the Scandi navian mineral. Analyses show :—Tribasic phosphate of lime, 65-91 per cent.; fluoride of lime, 7i ; chloride of lime, ; siliceous matters, 1-104 The deposits consist of pockets or bunches, of crystalline structure, embedded in granite, gneiss, and mica-slate. Their occurrence in widely separated pockets, the cost of excavation and hand-trimming from the accompanying rock, and the great expense of transportation, combine to limit their consumption. The production hitherto has not been much above 10,000 tons annually, even if it has always exceeded 5000 tons. New England and Great Britain absorb almost the whole quantity raised.
Phosphorite.—The mineral known as "phosphorite " is a fluor-apatite, contaminated with quartz, and differing from all other phosphates in being pyro-phosphorescent. It is found principally in Spain and Portugal, and especially in the Spanish province of Estramadura (whence its common name of " Estramadura phosphate"); also at Arnberg, in Bavaria. It is a hard, yellow-tinted, crystalline body, moderately free from iron and alumina, and often wanting altogether in carbonate of lime. It yields a high class superphosphate, from 30 to 33 per cent. of its phosphate being rendered soluble ; but the lack of carbonate of lime makes it non-porous, and difficult to get into a powdery condition. It is imported largely from Spain. Samples from cargoes indicate the following variations in its composition :—Tribasio phosphate of lime, 53-86 per cent.; carbonate of lime, fluoride of lime, 1-37; iron and alumina, l4-4; insoluble matters, 4-21. Logrosan and Caceres are the two principal localities where the mineral is found in Spain. At the former place, are several distinct veins of phosphorite. The rock is blasted out, and the large pieces are cleaned by hand and hammer, and then assorted into high and low grades. The pieces of trimmed rock average 3-4 in. in thickness. The shipment necessitates great trouble and expense. The mineral is transported in heavy waggons, drawn by mules or oxen, and carrying 2-27 tons, to the railway at Villanueva de la Serena. The cost of transport and handling till the phosphate is put on board at Lisbon amounts to almost 40s. a ton, and the expenses reach 60s. by the time it is landed in England. A railway to Villanueva would greatly reduce the cost, and would permit the delivery of enormous quantities of the material, to the exclusion of Carolina and other low-grade phosphates. This phosphorite may be depended on as yielding 75-85 per cent. of bone phosphate of lime, it can be raised and laid down at the mine's mouth for 12s. a ton, and it exists in enormous quantity. The construction of a railway or tramway as indicated would probably enable it almost to monopolize the markets of Europe.