During the last few years large quantities of phosphates have been imported from Florida. These are of different qualities, the land rocks now imported containing from 70 to 80 per cent of phosphate of lime, and the river phosphate about 60 per cent. The latter class are similar in composition to the best South Carolina river-phosphates, which they much resemble.
Lahn Phosphate.
Phosphate deposits were found at Nassau in Germany in 1864; but as the phosphate contained a considerable proportion of iron and alumina, they are not used in this country now, although they are in Germany for double superphosphate manufacture.
Bordeaux or French Phosphate.
Similar in quality to Lahn phosphate is that obtained in the neighbourhood of Bordeaux.
Algerian Phosphate.
Excellent phosphates are now being sent from Algeria—some cargoes being as rich as 70 per cent.
Crust Guanos.
We have already referred to the guanos in the chapter on Guano. They are also known under the name of Caribbean phosphates, and come from the West India Islands. The chief kinds are Aruba, Curaçao, Sombrero, and Navassa, the Great Cayman, Redonda, and Alta Vela. Most of them are of high quality, containing from 60 to 80 per cent of phosphate, and are thus suited for the manufacture of high-class superphosphates. Some of them, however, contain a considerable proportion of iron and alumina, and are not suitable for this purpose. The Redonda and Alta Vela phosphates consist chiefly of phosphate of alumina.
Value of Mineral Phosphates as a Manure.