COMMON ROCKFORMING MINERALS Georgia Southwestern .
Chemical Formula: Fe 2 O 3 (iron oxide) Mineral Group: oxides Luster/Color: nonmetallic (sometimes metallic)/redbrown Cleavage: absent Hardness: Other Characteristics: redbrown streak, high specific gravity (5), commonly associated with limonite, granular or massive aggregates . LIMONITE. Chemical Formula: Fe 2 O 3.