Okruschite is a rare calcium manganese beryllium arsenate that forms white imperfect, thick-tabular to blocky aggregates. It occurs in a hydrothermal vein cross-cutting rhyolite. It is associated with braunite and arseniosiderite. It was first described from Fuchs quarry, near Sailauf, Spessart Mountains, Bavaria, Germany.
Is this okruschite?
4-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 okruschite with a known reference. Okruschite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 3Match the color rangeCompare against the expected color range: white.
- 4Look at form & habitCrystal system: monoclinic. Typical habit: imperfect, thick-tabular to blocky aggregates.
Often confused with
Okruschite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Fillowite is the harder of the two (Mohs 4.5 vs. 3.5); luster reads vitreous on Okruschite and subresinous to greasy on Fillowite.
How to tell apart: Chladniite is the harder of the two (Mohs 4.5-5 vs. 3.5).
Often found alongside okruschite
Minerals reported to co-occur with okruschite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Mn²⁺₅Be₄(AsO₄)₆(OH)₄·6H₂O
- Mohs hardness
- 3.5
- Density
- 3.33 g/cm³
- Colors
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Imperfect, thick-tabular to blocky aggregates
- Cleavage
- Distinct on {010} and parting on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a hydrothermal vein cross-cutting rhyolite
Where rockhounds find okruschite
Classic worldwide localities
- Fuchs quarry, near Sailauf, Spessart Mountains, Bavaria, Germany
Field-hunting tip
Where it forms: In a hydrothermal vein cross-cutting rhyolite. If you start seeing braunite, mn-bearing calcite, arseniosiderite in float, you are in the right ground. Typical habit: imperfect, thick-tabular to blocky aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find okruschite on the map
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