Nordstrandite is a rare polymorph of aluminum hydroxide often occurring as tiny, thin tabular crystals. It is primarily found in vugs within alkaline igneous rocks and is highly prized by micromounters for its distinct triclinic crystal habit.
Is this nordstrandite?
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 nordstrandite with a known reference. Nordstrandite sits at Mohs 3, 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: vitreous, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: beige, colorless, light brown, light green, pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, aggregates.
Often confused with
Nordstrandite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside nordstrandite
Minerals reported to co-occur with nordstrandite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al(OH)₃
- Mohs hardness
- 3
- Density
- 2.41-2.43 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on cleavages
- Transparency
- Transparent to opaque
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals, aggregates
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Commonly in residual soils derived from limestones; in dolomitic oil shale, marine siltstone, chalk; in pegmatite, miarolitic cavities, and xenoliths in nepheline syenites
Where rockhounds find nordstrandite
Classic worldwide localities
- Green River Formation, Rio Blanco Co., Colorado, USA
- Gunong Kapor, near Bau, western Sarawak, Borneo, Malaysia
- Mt. Alifan-Mt. Lamlan ridge, south Guam
- Narssârssuk, Greenland
- Mont Saint-Hilaire, and in the Francon quarry, Montreal Island, Montreal, Quebec, Canada
- Princess sodalite mine, Bancroft, Ontario, Canada
Field-hunting tip
Where it forms: Commonly in residual soils derived from limestones; in dolomitic oil shale, marine siltstone, chalk; in pegmatite, miarolitic cavities, and xenoliths in nepheline syenites. If you start seeing quartz, kaolinite, diaspore in float, you are in the right ground. Typical habit: tabular crystals, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify nordstrandite?+
Where is nordstrandite found?+
What rocks look like nordstrandite?+
What minerals are found with nordstrandite?+
What kind of rock does nordstrandite form in?+
What is nordstrandite used for?+
Find nordstrandite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
