Tsumgallite is a rare gallium oxyhydroxide mineral first discovered in the oxidation zone of the famous Tsumeb Mine in Namibia. It typically forms as delicate, pale greenish yellow to beige acicular or radiating crystals associated with rare gallium-bearing sulfides. Due to its scarcity and origin, it is highly sought after by advanced mineral collectors specializing in rare species or Tsumeb minerals.
Is this tsumgallite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch tsumgallite with a known reference. Tsumgallite sits at Mohs 1.5-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: pale greenish yellow, biege.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates, irregular grains, micaceous.
Often confused with
Tsumgallite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Diaspore is the harder of the two (Mohs 6.5-7 vs. 1.5-2.5); luster reads pearly on Tsumgallite and adamantine, vitreous, pearly on cleavage faces on Diaspore.
How to tell apart: Goethite is the harder of the two (Mohs 5-5.5 vs. 1.5-2.5); streak differs, so Tsumgallite leaves white, Goethite leaves brownish yellow, yellow-orange, ocher-yellow; luster reads pearly on Tsumgallite and imperfect adamantine metallic to dull earthy; silky when fibrous on Goethite.
How to tell apart: Lepidocrocite is the harder of the two (Mohs 5 vs. 1.5-2.5); streak differs, so Tsumgallite leaves white, Lepidocrocite leaves dull orange; luster reads pearly on Tsumgallite and submetallic on Lepidocrocite.
Often found alongside tsumgallite
Minerals reported to co-occur with tsumgallite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- GaO(OH)
- Mohs hardness
- 1.5-2.5
- Density
- 5.08 g/cm³
- Colors
- Pale greenish yellowBiege
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates, irregular grains, micaceous
- Cleavage
- Perfect {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In vugs within tennantite-germanite ore from the oxidation zone
Where rockhounds find tsumgallite
Classic worldwide localities
- Tsumeb mine, Tsumeb, Namibia (type locality)
Field-hunting tip
Where it forms: In vugs within tennantite-germanite ore from the oxidation zone. If you start seeing söhngeite, zincian siderite, chalcocite in float, you are in the right ground. Typical habit: aggregates, irregular grains, micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
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Find tsumgallite on the map
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