Armbrusterite is a rare manganese-bearing silicate mineral found in alkaline igneous complexes. It typically presents as platy or tabular crystals and is notable for its distinct bright yellow fluorescence under short-wave ultraviolet light.
Is this armbrusterite?
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 armbrusterite with a known reference. Armbrusterite 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. Armbrusterite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Armbrusterite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, greenish-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, tabular aggregates.
Often confused with
Armbrusterite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside armbrusterite
Minerals reported to co-occur with armbrusterite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₅Na₆(Mn,Fe)₂Ti₂Si₁₆O₄₀(OH)₂·nH₂O
- Mohs hardness
- 3-4
- Density
- 2.68 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Tabular Aggregates
- Cleavage
- Perfect On {001}
- Fluorescence
- Bright Yellow Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find armbrusterite
Classic worldwide localities
- Khibiny Massif, Russia
- Lovozero Massif, Russia
Field-hunting tip
Look in alkaline pegmatites country, the host setting where armbrusterite typically forms. If you start seeing aegirine, microcline, nepheline in float, you are in the right ground. Field specimens usually show a platy crystals, tabular aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find armbrusterite on the map
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