Antigorite is a common member of the serpentine group, often appearing as massive or platy, foliated green aggregates. It is a primary constituent of serpentinite rocks and is typically found in altered ultramafic environments where magnesium-rich rocks have undergone metamorphism.
Is this antigorite?
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 antigorite with a known reference. Antigorite sits at Mohs 2.5-3.5, 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: resinous, greasy, silky, waxy, earthy.
- 4Match the color rangeCompare against the expected color range: green, yellow-green, brown, white, gray, bluish gray, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, platy, scaly.
Often confused with
Antigorite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads resinous, greasy, silky, waxy, earthy on Antigorite and silky on Chrysotile.
How to tell apart: Luster reads resinous, greasy, silky, waxy, earthy on Antigorite and waxy on Lizardite.
How to tell apart: Antigorite is noticeably harder (Mohs 2.5-3.5 vs. 1); luster reads resinous, greasy, silky, waxy, earthy on Antigorite and pearly, greasy, dull on Talc.
Often found alongside antigorite
Minerals reported to co-occur with antigorite. 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
- 2.5-3.5
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Resinous, greasy, silky, waxy, earthy
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, platy, scaly
- Cleavage
- Perfect on {001}, observed on {100} and {010}
- Rarity
- Common
- Uses
- Collector, Lapidary
- Host rock
- Commonly replaces ultramafic rocks, pervasively or in crosscutting veinlets
Where rockhounds find antigorite
Classic worldwide localities
- Texas, Lancaster Co., Pennsylvania, USA
- Baltimore, Baltimore Co., Maryland, USA
- Brewster, Putnam Co., New York, USA
- Buck Creek, Clay Co., North Carolina, USA
- Val Antigorio, Piedmont, Italy
- Prägraten, Tirol, Austria
Field-hunting tip
Where it forms: Commonly replaces ultramafic rocks, pervasively or in crosscutting veinlets. If you start seeing chromite, magnetite, chrysotile in float, you are in the right ground. Typical habit: massive, platy, scaly. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify antigorite?+
Where is antigorite found?+
What rocks look like antigorite?+
What minerals are found with antigorite?+
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Find antigorite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
