Identification

Sphalerite Identification Sheet

The principal zinc ore and a notorious deceiver: brilliant adamantine to resinous luster, six-direction cleavage, and a pale streak that gives it away.

Rock type: Hydrothermal

For: Collectors, Students

Mohs hardness 3, 4 3.5–4
Streak Pale yellow Brownish white to pale yellow
Luster Adamantine, Resinous, Greasy Adamantine, resinous to greasy
CleavagePerfect dodecahedral {011} (six directions)
Crystal habit Tetrahedral, Dodecahedral, Botryoidal, Granular, Massive Tetrahedra and dodecahedra, commonly twinned; also botryoidal, granular, and massive

Sphalerite (zinc sulfide) earned the old miners' name "blende" — deceiver — by looking like galena while yielding no lead. Its perfect dodecahedral cleavage flashes in six directions, the luster runs adamantine to resinous, and the streak is brownish white to pale yellow, far lighter than the specimen. Common with galena in hydrothermal veins.

Field identification workflow

  1. Tilt the specimen in the light: the adamantine-to-resinous flash from six cleavage directions is unlike galena's flat metallic planes.
  2. Streak it: brownish white to pale yellow from a crystal that may look nearly black. That mismatch is the diagnosis.
  3. Check heft against galena from the same vein — sphalerite is markedly lighter.
  4. Fresh surfaces can smell faintly of sulfur when scratched; old miners used the cue, and it still works.

Related in the library

Common lookalikes

Galena (grey-black streak, cubic cleavage, much heavier), magnetite (magnetic, black streak), cassiterite (much harder). The pale streak from a dark crystal is the giveaway.