Chapmanite is an extremely rare iron-antimony phyllosilicate mineral typically found as a secondary alteration product in hydrothermal veins. Collectors should look for its characteristic yellowish-green, powdery, or earthy coatings on quartz or metallic ores. It is primarily a collector's mineral due to its scarcity and distinct association with antimony-bearing deposits.
Is this chapmanite?
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 chapmanite with a known reference. Chapmanite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Chapmanite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Chapmanite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-green, green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: powdery, earthy, or as coatings.
Often confused with
Chapmanite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Chapmanite leaves yellow, Chlorite leaves white; luster reads dull on Chapmanite and pearly on Chlorite.
How to tell apart: Iron Ore is the harder of the two (Mohs 5-6.5 vs. 2.5); streak differs — Chapmanite leaves yellow, Iron Ore leaves reddish-brown to black; luster reads dull on Chapmanite and metallic to submetallic on Iron Ore.
Often found alongside chapmanite
Minerals reported to co-occur with chapmanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂Sb(Si₂O₅)(OH)₃
- Mohs hardness
- 2.5
- Density
- 3.9 g/cm³
- Streak
- Yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Powdery, Earthy, Or as Coatings
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $20-150 for small specimens
Where rockhounds find chapmanite
Classic worldwide localities
- Ontario, Canada
- Black Forest, Germany
- Sardinia, Italy
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where chapmanite typically forms. If you start seeing quartz, galena, arsenopyrite in float, you are in the right ground. Field specimens usually show a powdery, earthy, or as coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find chapmanite on the map
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