Asbestos typically refers to the fibrous, asbestiform habit of various minerals, most commonly chrysotile. It is characterized by its highly flexible, silky, and heat-resistant fibers, often found in parallel bundles within serpentinite rocks. Collectors should handle these specimens with extreme care to avoid fiber release.
Is this asbestos?
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 asbestos with a known reference. Asbestos sits at Mohs 2.5-3, 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: silky.
- 4Match the color rangeCompare against the expected color range: white, green, gray, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous.
Often confused with
Asbestos vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Tremolite is the harder of the two (Mohs 5-6 vs. 2.5-3); luster reads silky on Asbestos and vitreous on Tremolite.
How to tell apart: Actinolite is the harder of the two (Mohs 5-6 vs. 2.5-3); luster reads silky on Asbestos and vitreous, silky on Actinolite.
How to tell apart: Luster reads silky on Asbestos and resinous, greasy, silky, waxy, earthy on Antigorite.
Often found alongside asbestos
Minerals reported to co-occur with asbestos. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₃Si₂O₅(OH)₄
- Mohs hardness
- 2.5-3
- Density
- 2.5-2.6 g/cm³
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous
- Cleavage
- Perfect
- Rarity
- Common
- Uses
- Collector
- Host rock
- metamorphic serpentinite
Where rockhounds find asbestos
8 mapped spotsClassic worldwide localities
- Quebec, Canada
- Asbest, Russia
- Vermont, USA
- Arizona, USA
- Italy
Field-hunting tip
Where it forms: metamorphic serpentinite. If you start seeing magnetite, chromite, calcite in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in North Carolina, Connecticut, Georgia. Start trip planning there.
More asbestos photos
Common questions
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Find asbestos on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
