Fahleite is a very rare zinc iron calcium arsenate mineral that occurs as small, tabular, yellow crystals. It is almost exclusively found in the highly mineralized oxidation zone of the Tsumeb mine in Namibia, often associated with other rare secondary arsenates.
Is this fahleite?
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 fahleite with a known reference. Fahleite sits at Mohs 2, 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: silky or pearly.
- 4Match the color rangeCompare against the expected color range: gray, gray green, light green, straw yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates, fibrous.
Often confused with
Fahleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Hopeite is the harder of the two (Mohs 3.5 vs. 2); luster reads silky or pearly on Fahleite and vitreous, pearly on {010} cleavages on Hopeite.
How to tell apart: Parahopeite is the harder of the two (Mohs 3.5-4 vs. 2); luster reads silky or pearly on Fahleite and vitreous, pearly on cleavages on Parahopeite.
How to tell apart: Legrandite is the harder of the two (Mohs 4.5 vs. 2); luster reads silky or pearly on Fahleite and vitreous on Legrandite.
Often found alongside fahleite
Minerals reported to co-occur with fahleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaZn₅Fe₂(AsO₄)₆·14H₂O
- Mohs hardness
- 2
- Density
- 3.08 g/cm³
- Streak
- White
- Luster
- Silky or pearly
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates, fibrous
- Cleavage
- One, perfect, ⊥ fiber length
- Rarity
- Rare
- Uses
- Collector
- Host rock
- On oxidized tennantite–chalcocite ore from a deep oxidized zone of a dolostone-hosted hydrothermal polymetallic ore deposit
Where rockhounds find fahleite
Classic worldwide localities
- Tsumeb, Namibia
Field-hunting tip
Where it forms: On oxidized tennantite–chalcocite ore from a deep oxidized zone of a dolostone-hosted hydrothermal polymetallic ore deposit. If you start seeing lavendulan, cuprian adamite, conichalcite in float, you are in the right ground. Typical habit: aggregates, fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fahleite?+
Where is fahleite found?+
Is fahleite safe to handle?+
What rocks look like fahleite?+
What minerals are found with fahleite?+
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Find fahleite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
