Windhoekite is a rare phyllosilicate mineral found primarily in alkaline igneous environments. It typically forms as thin, pearly yellowish brown crusts or delicate aggregates on the surfaces of associated minerals like sodalite in pegmatite cavities.
Is this windhoekite?
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 windhoekite with a known reference. Windhoekite 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: beige.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous or silky.
- 4Match the color rangeCompare against the expected color range: yellowish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts.
Often confused with
Windhoekite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside windhoekite
Minerals reported to co-occur with windhoekite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Fe₂.₆₇(Si₈O₂₀)(OH)₄·10H₂O
- Mohs hardness
- 2
- Density
- 2.62 g/cm³
- Colors
- Streak
- Beige
- Luster
- Vitreous or silky
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In miarolitic cavities in alkaline phonolite
Where rockhounds find windhoekite
Classic worldwide localities
- Ariskop Quarry, Aris, near Windhoek, Khomas Region, Namibia
Field-hunting tip
Where it forms: In miarolitic cavities in alkaline phonolite. If you start seeing fluorapophyllite, aegirine, microcline in float, you are in the right ground. Typical habit: platy crystals, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify windhoekite?+
Where is windhoekite found?+
What rocks look like windhoekite?+
What minerals are found with windhoekite?+
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What is windhoekite used for?+
Find windhoekite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
