Zultanite's 6.5–7 Mohs hardness measures scratch resistance, not toughness. Toughness — resistance to chipping and cleaving under impact — is rated only "fair" for diaspore because of its perfect {010} cleavage. A daily-wear ring made from a stone with weak toughness will eventually chip even if the surface remains unscratched. This is why Zultanite is best suited to pendants and earrings than rings.

The measurement

Industry-standard toughness rating (poor / fair / good / excellent) is the standard method documented in laboratory reference texts. Diaspore-specific values are documented across the property guides; this entry focuses on the practical implications.

Implications for buyers and graders

The value above is part of the verified mineralogical baseline editors apply when grading or authenticating a stone. Discrepancies from this baseline are documented case-by-case in laboratory reports and should be flagged before transaction.

Where this fits in the larger archive

See the related property guides for adjacent measurements and the cluster-support articles for practical applications.