Clinohumite is a rare magnesium silicate mineral found primarily in contact metamorphic zones of carbonate rocks. Collectors prize it for its vibrant yellow-to-orange hues and its tendency to display strong yellow fluorescence under longwave ultraviolet light.
Is this clinohumite?
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 clinohumite with a known reference. Clinohumite sits at Mohs 6, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow, brown, white, orange, reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, granular, massive.
Often confused with
Clinohumite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside clinohumite
Minerals reported to co-occur with clinohumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₉(SiO₄)₄F₂
- Mohs hardness
- 6
- Density
- 3.17-3.35 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, granular, massive
- Cleavage
- {100}, poor
- Fluorescence
- Often fluoresces yellow under LW UV
- Rarity
- Rare
- Uses
- Collector, Gemstone
- Host rock
- In contact metamorphic zones in dolostones and metasomatized limestones adjacent to felsic plutonic rocks; in serpentine and talc schists; in a carbonatite
Where rockhounds find clinohumite
1 mapped spotsClassic worldwide localities
- Tilly Foster iron mine, Brewster, Putnam Co., New York, USA
- Buell Park, near Fort Defiance, Apache Co., Arizona, USA
- Crestmore, Riverside Co., and the Twin Lakes region, Fresno Co., California, USA
- Monte Somma and Vesuvius, Campania, and Franscia, Val Malenco, Lombardy, Italy
- Hämeenkylä and Ojamo, Lohja, Finland
- Broadford, Isle of Skye, Scotland
Field-hunting tip
Where it forms: In contact metamorphic zones in dolostones and metasomatized limestones adjacent to felsic plutonic rocks; in serpentine and talc schists; in a carbonatite. If you start seeing grossular, wollastonite, forsterite in float, you are in the right ground. Typical habit: prismatic crystals, granular, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
How do you identify clinohumite?+
Where is clinohumite found?+
Can I find clinohumite in the United States?+
What rocks look like clinohumite?+
What minerals are found with clinohumite?+
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Find clinohumite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
