Calcareous rock mass

Phosphorite, for our purposes, is the term applied to calcium phosphate rocks, whether they are accumulations of bones, precipitates directly from sea water or replacements of calcareous rocks. They are very extensive on the earth, occurring on all continental land masses with the possible exception of Antarctica, where commercial deposits have not yet been found. Phosphorites comprise the principal geologic storage bin for inorganic phosphates. 

Reduction in mass of the parent rock by leaching, at approximately constant volume. Normally this reduction is less than 50 wt.%, but greater reductions from calcareous and/or feldspathic rocks, locally to lesser volumes, are possible. Titanium-oxide minerals are hence residually enriched. 

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