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, so 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, so 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, 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
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
