Distribution of Phosphatic Rocks

Great Britain

The deposits are of historic interest only, in view of the abundant high-grade rock which is imported. The nodular deposits of the Eastern counties, known as coprolites, contain the remains of the teeth and bones of fish and reptiles. The richer beds contain a satisfactory percentage of phosphate, as is evident from the following analysis:—

	Lyme Regis.	Cambridge	Suffolk.
Calcium phosphate, per cent	60.77	77.7	56.0	70.9
Calcium carbonate, per cent.	28.67	2.3	10.0	10.3

The fossil bone bed at Sutton (Suffolk) once contained 50 to 60 per cent, of calcium phosphate, but the remaining deposits are of much poorer quality.

The working of the English beds has long been discontinued, except that during the Great War some thousands of tons of coprolites were mined at Trumpington, Cambridge, and in Suffolk.

Europe

Useful deposits are found in France, Germany, Czechoslovakia, Poland, Belgium and Spain, the deposits of Estremadura in the last-named country being inspected by Dr Daubeny as early as 1843.

France

Phosphatic limestones are found in the Pas de Calais, Meuse and Somme regions, and the last-named deposits were among the earliest to be worked. Specimens have been found which contain up to 78 per cent, of calcium phosphate. Those from the Meuse and the Ardennes contain about 40 per cent. A limestone with less than 30 per cent, of calcium phosphate is hardly considered worth using for the manufacture of superphosphate. France also controls the output of North Africa.

North Africa

The deposits of Algiers were discovered in 1873 and were fully reported upon in 1886. They are of Eocene age and contain 58 to 68 per cent. of calcium phosphate in a soft rock, together with marl, considerable amounts of silica, calcium fluoride and chloride, nodules of gypsum and almost pure limestone. The beds usually are several feet thick and run continuously from Morocco to Egypt at a distance of over 100 miles from the sea. Those at Constantine (Algiers) are 120 miles from the port of Bona, and those at Gafsa (Tunis) 150 miles from the port of Sfax.

The potential resources in this region have not yet been fully explored but are probably the greatest which have been discovered up to the present. It has been estimated that there are 1000 million tons available in Morocco. This estimate has recently been increased to 3000 million metric tons.

United States

The principal deposits are in South Carolina, Florida, Tennessee, Arkansas, Utah and Wyoming. The South Carolina deposits are of Miocene age and occur both as " land " and " river " rock. They contain 25 to 28 per cent, of phosphoric oxide and 35 to 42 per cent, of lime. They were the earliest to be exploited, namely, from 1868 onwards, and in 1893 they furnished about one-fifth of the world's supply. Since this date the production has declined, while that of Florida has greatly increased. In 1913 Florida and Tennessee together produced some 96 per cent, of the total output from the United States of America. The hard-rock deposits of Florida are of Tertiary age, and they run parallel to the coast for 144 miles. After concentration by mechanical means they contain usually from 77 to 79 per cent, of calcium phosphate (more rarely up to 82 per cent.) with 3 per cent, of oxides of iron and alumina, some calcium fluoride and other constituents, and 3 per cent, of moisture. The best grades of Tennessee rock were guaranteed to contain 72 per cent, of calcium phosphate, and 65 per cent, is common. The soft rock is a phosphatic clay. The river pebbles are dark grey to black and are very cheaply obtained by dredging.

Deposits are found also in Canada, the West Indies, Mexico and South America.

The amounts of phosphate rock mined annually increased only slowly from the beginnings of the industry in 1847 to 250,000 tons in 1869, then to about one million tons in 1887 and about seven million tons in 1913.

After the great fluctuations during the Great War and post-War years, the production had again reached four million tons in 1919 and seven million tons in 1920, made up as follows (round numbers):—

	Tons
United States of America	3,000,000
North Africa	3,000,000
Oceanic Islands	500,000
Other Countries	500,000
Total	7,000,000

The greater part of the increase is due to the North African deposits. The yearly production from these sources is now greater than that which is obtained from the North American deposits.

It has been estimated that the available phosphate deposits would last for a century, but this estimate does not fully take into account the North African deposits or the proportion which will be conserved and returned to the soil by future generations. The present annual requirements of a great agricultural country like France or Germany appear to be of the order of a million tons.