Andyrobertsite is an extremely rare arsenate mineral found almost exclusively in the oxidation zones of the Tsumeb Mine. It typically forms delicate, radiating clusters of white or pale yellow crystals that are highly sought after by advanced systematic collectors.
Is this andyrobertsite?
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 andyrobertsite with a known reference. Andyrobertsite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Andyrobertsite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Andyrobertsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular to lath-like crystals in radiating sprays.
Often confused with
Andyrobertsite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Andyrobertsite leaves white, Lavendulan leaves pale blue.
How to tell apart: Andyrobertsite is noticeably harder (Mohs 3-4 vs. 1.5-2); streak differs — Andyrobertsite leaves white, Tyrolite leaves pale green; luster reads vitreous on Andyrobertsite and pearly on Tyrolite.
Often found alongside andyrobertsite
Minerals reported to co-occur with andyrobertsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCu₅Cd(AsO₄)₄(AsO₂OH)₂·2H₂O
- Mohs hardness
- 3-4
- Density
- 3.37 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular to Lath-like Crystals in Radiating Sprays
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Mineral Deposits
- Typical price
- $100-500 thumbnail
Where rockhounds find andyrobertsite
Classic worldwide localities
- Tsumeb Mine, Namibia
Field-hunting tip
Look in hydrothermal mineral deposits country — that is the host setting where andyrobertsite typically forms. If you start seeing tumsite, cuproadamite, tennantite in float, you are in the right ground. Field specimens usually show a acicular to lath-like crystals in radiating sprays habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find andyrobertsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
