Tremolite is a calcium magnesium silicate commonly found in metamorphosed carbonate rocks. It typically forms elongate, prismatic crystals or fibrous masses, and can sometimes transition into the iron-rich variety actinolite. Collectors should be aware that fibrous habits may present as asbestos, requiring careful handling.
Is this tremolite?
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 tremolite with a known reference. Tremolite sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tremolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Tremolite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, gray, green, brown, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, fibrous, bladed, columnar.
Often confused with
Tremolite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside tremolite
Minerals reported to co-occur with tremolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Mg₅Si₈O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 2.9-3.0 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Fibrous, Bladed, Columnar
- Cleavage
- Perfect Prismatic
- Rarity
- Common
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphic Rocks Like Marble and Schist
- Typical price
- $5-50 thumbnail, $30-200 cabinet specimen
Where rockhounds find tremolite
12 mapped spotsClassic worldwide localities
- Campolungo, Switzerland
- Pierrepont, New York, USA
- Sudbury, Ontario, Canada
- Piedmont, Italy
- Afghanistan
Field-hunting tip
Look in metamorphic rocks like marble and schist country — that is the host setting where tremolite typically forms. If you start seeing calcite, dolomite, talc in float, you are in the right ground. Field specimens usually show a prismatic crystals, fibrous, bladed, columnar habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, New Jersey, New York — start trip planning there.
Common questions
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Find tremolite on the map
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