No new deposits have lately been discovered in these regions, despite continued and careful prospecting ; and an impression prevails that the better part, both in quality and quantity, has already been sent to market. The production has reached 20,000 tons a year.
The German or Nassau phosphate occurs in a manner very similar to the last-named, near the rivers Lahu and Dill, in the Rhine basin. It is also equally variable in composition and aspect ; sometimes it breaks with an earthy fracture, and is of yellow hue ; again it will occur as a phos phatic concrete, cemented by ferruginous matter ; and the crystalline form is not unknown. The best sorts are fairly free from iron, and make a good dry superphosphate ; but they set extremely hard. For a time, they were abundantly used here, but the supply is now trifling. The lower qualities, like those of the Bordeaux mineral, are useless for manure-making, and for identical reasons. They are similarly employed in a raw state on the spot. The better classes have a varying constitulion, as :—Tribasic phosphate of lime, 58-71 per cent. ; carbonate ; iron and alumina, 4f-l5 ; insoluble matters, 2i-12. It possesses a distinctive peculiarity in the presence of appreciable quantities of iodine, which is often driven off in violet vapours, on the addition of sulphuric acid.
South Carolina or Charlestown phosphate is very similar in composition to the best coprolites, but differs widely from them in appearance. It is found in the calcareous formation of the Charles town basin, partly underlying the city, and occupying an area amounting altogether to perhaps 50-60 square miles. The deposits are distinguished as "land " and " river," each having its own peculiarities. The mineral occurs in rough nodules, perforated by boring molluscs, and associated with marine and terrestrial animal fossils, in thick strata of clay and sand, the cavities in the phosphate being mechanically filled with these substances, from which they can be cleansed by washing. The phosphate appears to be a converted Eocene mar], and is very uniform in composition. The river phosphate is of dark-grey colour, and is obtained by dredging in the Bull, Soosaw, and Storm river beds. It is much the harder of the two varieties, and is difficult to grind ; but is very superior for superphosphate-making. Though not containing so much phosphoric acid as the best Cambridge
coprolites, it is distinctly preferable to them, ou account of its much lower percentage of carbonate of lime consuming less acid ; also by reason of the pyritous nature of nearly all the iron, and from its possessing physical characters which enable the acid to act on it with much better effect. It has replaced Cambridge coprolitea to a, great extent in this country. Its composition is represented as follows :—Tribasic phosphate of lime, 54-58 per cent.; carbonate of lime, 122-14 ; fluoride of lime, 1-2f ; iron and alumina, 3f ; insoluble matters, 14-15. It is now often dried in hot-air flues before exportation, and is then called "calcined phosphate," yielding:—Tribasic phosphate of lime, 57f-59 per cent.; carbonate of lime, 112 ; siliceous matters, 122. The land phosphate is inferior to the other in most respects, and is consumed almost entirely in home markets. It has a yellowish colour, and is softer, and more easily ground ; but more difficulty and expenditure are entailed in cleansing it than is needed with the river kind, which can be washed at the same moment that it is dredged up. For this reason also, combined with the presence of its iron as oxide, it yields a lower grade of soluble phosphate, and is consequently lees valuable. The mean of eleven estimations gives :—Tribasic phosphate of lime, 53f per cent.; carbonate of lime, 8/ ; iron and alumina, 74 ; siliceous matters, 14.
Russia is said to possess some 12,000 square miles of phosphate-producing country, but analysis indicates nothing higher than 33 per cent, of tribasic phosphate. In the Bukowina, also, there are some deposits, declared to be rich on the average. The Russian phosphate occurs generally in the strata of the Cretaceous formation ; it is also found in the Jurassic, Tertiary, and even Silurian. An examination into its commercial value led to the conclusion that, where the phosphate is accessible, its quality is too low to admit of more than local utilization ; while the richer nodules, disseminated as they are throughout a compact fdrmation, cannot be mined profitably. Only one attempt has been made at local agricultural utilization of these vast deposits: that ended in failure.