Brucite is a magnesium hydroxide mineral known for its distinct pearly luster and flexible, sectile nature. It typically forms as foliated masses or tabular crystals in hydrothermal veins and altered serpentinites, making it a key indicator of low-temperature metamorphic conditions.
Is this brucite?
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 brucite with a known reference. Brucite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: waxy, pearly on cleavage surfaces.
- 4Match the color rangeCompare against the expected color range: white, blue, gray, gray blue, yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: fibrous, massive.
Often confused with
Brucite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Brucite is noticeably harder (Mohs 2.5 vs. 1); luster reads waxy, pearly on cleavage surfaces on Brucite and pearly, greasy, dull on Talc.
How to tell apart: Luster reads waxy, pearly on cleavage surfaces on Brucite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Luster reads waxy, pearly on cleavage surfaces on Brucite and greasy on Serpentine.
Often found alongside brucite
Minerals reported to co-occur with brucite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg(OH)₂
- Mohs hardness
- 2.5
- Density
- 2.39 g/cm³
- Streak
- White
- Luster
- Waxy, pearly on cleavage surfaces
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Fibrous, massive
- Cleavage
- {0001}, perfect
- Rarity
- Common
- Uses
- Collector, Industrial
- Host rock
- A common alteration of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphic limestones and chlorite schists; formed during serpentinization of dunites
Where rockhounds find brucite
7 mapped spotsClassic worldwide localities
- Hoboken, Hudson Co., New Jersey, USA
- Wood’s Chrome mine, near Texas, Lancaster Co., Pennsylvania, USA
- Tilly Foster mine, Brewster, Putnam Co., New York, USA
- A Gabbs, Gabbs district, Nye Co., Nevada, USA
- Asbestos and Wakefield, Quebec, Canada
- Mt. Vesuvius, Campania, and at Teulada, Sardinia, Italy
Field-hunting tip
Where it forms: A common alteration of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphic limestones and chlorite schists; formed during serpentinization of dunites. If you start seeing calcite, aragonite, dolomite in float, you are in the right ground. Typical habit: fibrous, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Maryland, Pennsylvania, New York. Start trip planning there.
More brucite photos
Common questions
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Find brucite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
