Tenacity describes how a mineral responds to stress—whether it bends, breaks, flakes, cuts, or deforms. Terms like brittle, malleable, sectile, flexible, and elastic describe behaviors you can observe during careful handling or testing of small fragments. Collectors use tenacity to separate minerals with similar appearance, especially among metallic species. Because testing can damage a specimen, tenacity is best checked on already-broken chips or tiny fragments.
To assess Tenacity safely, avoid testing on a display-quality specimen; use a chip, edge fragment, or already-damaged piece. Write down exactly what you did (“bent slightly then snapped,” “cut with a knife into curls,” “crumbled under light pressure”) so your note is reproducible. Combine tenacity with hardness because they describe different behaviors—hard minerals can still be brittle, and softer metals can be malleable. Tenacity notes are especially useful when luster and color are not enough to separate candidates.
Tenacity vs. hardness Hardness is scratch resistance. Tenacity is bending/breaking/deforming behavior under stress.
Tenacity vs. brittle fracture only Tenacity includes malleable and sectile behaviors, not just breaking patterns.
Tenacity vs. weathered crumbly surfaces Weathering can make a mineral crumble. Test a fresh interior fragment when possible.
Tenacity vs. testing on a display specimen Tenacity tests can damage the piece. Use a chip or fragment instead of the main specimen.