Eyselite is a rare iron germanium hydroxide. Associated minerals include renierite, germanite and tennantite. It was first described from Tsumeb mine, Tsumeb, Namibia.
Is this eyselite?
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 eyselite with a known reference. Eyselite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dirty brown yellow, tan yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates, bladed.
Often confused with
Eyselite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Eyselite is noticeably harder (Mohs 3 vs. 2); streak differs, so Eyselite leaves brownish yellow, Tellurite leaves white; luster reads vitreous on Eyselite and subadamantine on Tellurite.
How to tell apart: Emmonsite is the harder of the two (Mohs ~5 vs. 3); streak differs, so Eyselite leaves brownish yellow, Emmonsite leaves pale yellow.
Often found alongside eyselite
Minerals reported to co-occur with eyselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺Ge⁴⁺₃O₇(OH)
- Mohs hardness
- 3
- Density
- 3.639 g/cm³
- Colors
- Dirty brown yellowTan yellow
- Streak
- Brownish yellow
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates, bladed
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed by groundwater in a vug on a single specimen of renierite-germanite-tennantite ore from the oxidation zone above a polymetallic sulfide mineral deposit
Where rockhounds find eyselite
Classic worldwide localities
- Tsumeb mine, Tsumeb, Namibia
Field-hunting tip
Where it forms: A secondary mineral formed by groundwater in a vug on a single specimen of renierite-germanite-tennantite ore from the oxidation zone above a polymetallic sulfide mineral deposit. If you start seeing renierite, germanite, tennantite in float, you are in the right ground. Typical habit: aggregates, bladed. Train your eye for that shape before scanning the outcrop.
Common questions
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Find eyselite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
