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, 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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What rocks look like jimthompsonite?+
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Find jimthompsonite on the map
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