Identification: Staurolite is a complex iron, aluminum silicate, Fe2Al9Si4O22(OH)2. It is usually some shade of brown, has a colorless streak, a specific gravity that ranges from 3.4 to 3.8 and a hardness of 7.0 to 7.5. Staurolite resembles rutile under the microscope, but has a dull luster, In Florida, staurolite occurs as rounded sand-size particles.

Occurrence: Staurolite is one of the most abundant minerals in Florida's heavy sand deposits.

Use: The principal use of staurolite is in the production of Portland cement, where it substitutes for clay in supplying the necessary alumina and part of the iron as required by the cement formula. Staurolite is also used as a sand blasting material.