 It has a Mohs hardness of 5.5 and a specific gravity of 3.28 - 3.33.Under short wave ultraviolet light it fluoresces a rich orange color.It is frequently associated with minerals such as hardystonite (fluoresces violet blue), esperite (fluoresces bright yellow), calcite (fluoresces orange-red), franklinite (non-fluorescent) and willemite (fluoresces green).