1. n. [Drilling Fluids]
A group of minerals and inorganic compounds made up of iron that is in +2 (ferrous) and +3 (ferric) valence states and oxygen in the –2 valence state, such as ferrous oxide, FeO, and ferric oxide, Fe2O3. Fe3O4 is a mixture of ferric oxide and ferrous oxide that commonly occurs in a fine-grained, magnetic crystalline form. Hematite, Fe2O3, the most common iron oxide, exists in several crystalline forms. Other forms of hematite are too abrasive to use as weighting material in drilling fluids.
See: abrasion test, barite, hematite, scavenger, sulfide, weighting material