Luster is not a diagnostic property. This means that, for most mineral species, luster can vary from one specimen to another.

For example: hematite can exhibit a metallic luster, a submetallic luster, or a dull luster. A single specimen can exhibit one or more of these lusters.

Because of that, luster cannot be heavily relied upon in mineral identification. It might be considered to be a “hint” that can set a person on the proper route.