Nickelalumite is a rare secondary mineral found in the oxidation zones of nickel-rich ore deposits. Collectors typically search for its distinct blue to blue-green platy or micaceous crusts, often associated with other secondary copper and nickel species.
Is this nickelalumite?
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 nickelalumite with a known reference. Nickelalumite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: bluish white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: sky blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations, nodular.
Often confused with
Nickelalumite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Nickelalumite leaves bluish white, Woodwardite leaves light blue.
How to tell apart: Zaratite is the harder of the two (Mohs 3.5 vs. 2.5); streak differs, so Nickelalumite leaves bluish white, Zaratite leaves light green; luster reads pearly on Nickelalumite and vitreous to greasy on Zaratite.
Often found alongside nickelalumite
Minerals reported to co-occur with nickelalumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NiAl₄(SO₄)(OH)₁₂·3H₂O
- Mohs hardness
- 2.5
- Density
- 2.24 g/cm³
- Colors
- Streak
- Bluish white
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations, nodular
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Crusts on gypsum crystals
Where rockhounds find nickelalumite
Classic worldwide localities
- Mbobo Mkulu cave, eastern Transvaal, South Africa (type locality)
Field-hunting tip
Where it forms: Crusts on gypsum crystals. If you start seeing gypsum, goethite, malachite in float, you are in the right ground. Typical habit: encrustations, nodular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify nickelalumite?+
Where is nickelalumite found?+
Is nickelalumite safe to handle?+
What rocks look like nickelalumite?+
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Find nickelalumite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
