124 DEPOSITS OF PHOSPHATE OF LIME. [bull. 46. 
geneous deposit of a white or yellow color. It contains 75 to 80 per cent, 
of phosphate of lime. Many bones occur, and at times the deposit takes 
the form of a real bone breccia. The principal rock of the island is a 
palagonite tufa, filled with shells and bones. 
The Navassa phosphate is found on an uninhabited island, consisting 
of a terrace encircled by a high plateau. The phosphate is found in 
pockets in the living coral, and in the numerous depressions and hollows 
on the island. It is of a dark brown color, and is composed of a hard 
mass of oolitic grains. It contains 10 to 15 per cent, of alumina and 
oxide of iron (Meyn), and is therefore not very popular as a source of 
superphosphate, as it makes a sticky product. 
The phosphate of Aruba Island is of a hard, massive variety, and is 
white to dark brown in color. Occasionally the underlying coral on this 
island, as well as on many others in both the West Indies and the Pa- 
cific Ocean, has been phosphatized by the infiltration of the soluble 
parts of the original guano deposits. Thus at Aruba large masses of 
coral, containing 70 to 75 per cent, phosphate of lime, are found. 
Several distinct phosphate minerals occur in pockets in the phosphate 
beds in the West Indies. One of them, known as pyrophosphorite, was 
described by Dr. 0. U. Shepard, jr., in the American Journal of Science, 
January, 1878. It is snow white, amorphous, opaque, and has a fracture 
like magnesite. It has a hardness of 3 to 3.5, and a specific gravity of 
2.50 to 2.53. It is essentially an ortho pyrophosphate of lime with 
pyrophosphate of magnesia, and has the formula Mg 2 P 2 7 +4(Ca 3 P 2 Q 8 , 
Ca 2 P 2 7 ). 
On the islands of Mona and Moneta, in the West Indies, occur the 
minerals monite and monetite. They were described and named by 
Prof. C. U. Shepard, sr., in the American Journal of Science, May, 1882. 
The monetite occurs as a crystalline mineral, of a white or brown color, 
in association with monite, which is a white, soft, incoherent mass. 
Mouetite is a crystallized dicalcic ortho-phosphate and has the formula 
CaHP0 4 . Monite has the formula Ca 3 P 2 8 +H 2 0. 
Deposits of leached guano have been found on several islands in the 
Gulf of California. The deposit on Raza Island averaged over 41 per 
cent, of phosphoric acid, which corresponds to over 85 per cent, of phos- 
phate of lime. (See analyses.) The beds in this island have been 
exhausted. 
The deposits of the West Indies supply most of the leached guano 
now sold. Curacoa annually produces 50,000 to 70,000 tons, and Som- 
brero about 10,000. The other islands produce much less. The Pacific 
Ocean islands are, at present, little worked. The difficulty with many 
of the West India deposits is that they contain large quantities of phos- 
phate of iron and alumina, which make them very undesirable as sources 
of superphosphate. On some of the islands there occur beds of almost 
pure phosphate of iron and alumina. 
(598) 
