Jimthompsonite is a rare chain silicate mineral often associated with anthophyllite in altered ultramafic rocks. It is best identified by its distinct bladed to fibrous habit and characteristic pinkish-brown color, often requiring X-ray diffraction to distinguish it definitively from associated pyroxene-group minerals.
Is this jimthompsonite?
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 jimthompsonite with a known reference. Jimthompsonite 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. Jimthompsonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Jimthompsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, brown, yellowish-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: bladed crystals, fibrous aggregates.
Often confused with
Jimthompsonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside jimthompsonite
Minerals reported to co-occur with jimthompsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mg,Fe)₅Si₆O₁₆(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.4 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Bladed Crystals, Fibrous Aggregates
- Cleavage
- Perfect in Two Directions
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Ultramafic Rocks
- Typical price
- $20-150 for small specimens
Where rockhounds find jimthompsonite
Classic worldwide localities
- Vermont, USA
- Norway
- Finland
- Italy
Field-hunting tip
Look in metamorphic ultramafic rocks country — that is the host setting where jimthompsonite typically forms. If you start seeing anthophyllite, talc, magnetite in float, you are in the right ground. Field specimens usually show a bladed crystals, fibrous aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jimthompsonite?+
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How much is jimthompsonite worth?+
What rocks look like jimthompsonite?+
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Find jimthompsonite on the map
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