Montebrasite is a lithium-rich phosphate mineral occurring primarily in granitic pegmatites. It is often found as massive, cleavable blocks and is visually indistinguishable from amblygonite without chemical analysis, as they form a continuous solid solution series.
Is this montebrasite?
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 montebrasite with a known reference. Montebrasite sits at Mohs 5.5-6, 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: bluish, colorless, greenish, greenish gray, gray white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: massive, prismatic.
Often confused with
Montebrasite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside montebrasite
Minerals reported to co-occur with montebrasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- LiAlPO₄(OH)
- Mohs hardness
- 5.5-6
- Density
- 2.98-3.04 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on cleavages
- Transparency
- Translucent to transparent
- Crystal system
- Triclinic
- Crystal habit
- Massive, prismatic
- Cleavage
- Perfect on {100}; good on {110}; distinct on {011} [morphological orientation of ref. (1)]
- Rarity
- Uncommon
- Uses
- Collector, Lithium source
- Host rock
- A late primary and secondary mineral in zoned granite pegmatites; may be an ore of lithium
Where rockhounds find montebrasite
Classic worldwide localities
- Nevel quarry and Bell Pit, Newry, Oxford Co., Maine, USA
- Midnight Owl pegmatite, White Picacho district, Maricopa Co., Arizona, USA
- Peerless and Hugo mines, near Keystone, Pennington Co., South Dakota, USA
- Custer, Custer Co., at the Tip Top and Tin Mountain mines, Beecher lode, eight km southeast of Custer, South Dakota, USA
- Montebras, Creuse, France
- Varuträsk pegmatite, 15 km northwest of Skellefteå, Västerbotten, Sweden
Field-hunting tip
Where it forms: A late primary and secondary mineral in zoned granite pegmatites; may be an ore of lithium. If you start seeing hydroxylapatite, spodumene, lepidolite in float, you are in the right ground. Typical habit: massive, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify montebrasite?+
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What rocks look like montebrasite?+
What minerals are found with montebrasite?+
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Find montebrasite on the map
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