Revenues of this tiny island have traditionally come from exports of phosphate rock.

Polk continued to lead the state in 1998, with 14.7 million tons of phosphate rock mined.

Their investigations also produced the "superphosphate", consisting in the acid treatment of phosphate rock.

In this method, phosphate rock is used, and more than 100 million tonnes are processed annually.

Uranium occurs at concentrations of 50 to 200 parts per million in phosphate-laden earth or phosphate rock.

However, her superstructure and cargo of phosphate rock appear to have been salvaged.

Phosphates occur widely in nature mostly as phosphate rock or fluorapatite.

It is also found in the earth as phosphate rock.

There are important deposits of phosphate rock in a number of areas.

A less pure form is made by reacting sulfuric acid with phosphate rock.