Clinojimthompsonite is a rare chain silicate mineral that forms as a structural variation of jimthompsonite. It is typically found in association with other magnesium silicates in altered ultramafic rocks and is often difficult to distinguish from its orthorhombic counterpart without X-ray diffraction analysis.
Is this clinojimthompsonite?
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 clinojimthompsonite with a known reference. Clinojimthompsonite sits at Mohs 2-2.5, 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: silky to pearly.
- 4Match the color rangeCompare against the expected color range: colorless, pink brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Clinojimthompsonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Anthophyllite is the harder of the two (Mohs 5.5-6 vs. 2-2.5); luster reads silky to pearly on Clinojimthompsonite and vitreous, pearly on cleavage on Anthophyllite.
How to tell apart: Clinojimthompsonite is noticeably harder (Mohs 2-2.5 vs. 1); luster reads silky to pearly on Clinojimthompsonite and pearly, greasy, dull on Talc.
Often found alongside clinojimthompsonite
Minerals reported to co-occur with clinojimthompsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₅Si₆O₁₆(OH)₂
- Mohs hardness
- 2-2.5
- Density
- 3.02 g/cm³
- Colors
- Streak
- White
- Luster
- Silky to pearly
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- {110} predicted from the structure
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the black wallrock between chlorite and actinolite zones of a metamorphosed ultramafic body
Where rockhounds find clinojimthompsonite
Classic worldwide localities
- Carleton talc quarry, near Chester, Windsor Co., Vermont, USA
Field-hunting tip
Where it forms: In the black wallrock between chlorite and actinolite zones of a metamorphosed ultramafic body. If you start seeing chesterite, clinojimthompsonite, anthophyllite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify clinojimthompsonite?+
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What rocks look like clinojimthompsonite?+
What minerals are found with clinojimthompsonite?+
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Find clinojimthompsonite on the map
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