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. Streak: greenish yellow to deep yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: nonmetallic.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish green, olive green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: earthy, granular.
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 greenish yellow to deep yellow, Chlorite leaves white; luster reads nonmetallic on Chapmanite and pearly on Chlorite.
How to tell apart: Goethite is the harder of the two (Mohs 5-5.5 vs. 2.5); streak differs, so Chapmanite leaves greenish yellow to deep yellow, Goethite leaves brownish yellow, yellow-orange, ocher-yellow; luster reads nonmetallic on Chapmanite and imperfect adamantine metallic to dull earthy; silky when fibrous on Goethite.
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)O₃(OH)
- Mohs hardness
- 2.5
- Density
- 3.69-3.75 g/cm³
- Streak
- Greenish yellow to deep yellow
- Luster
- Nonmetallic
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Earthy, granular
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In veinlets cutting gneisses containing varying amounts of graphite (Smilkov, Czech Republic)
Where rockhounds find chapmanite
Classic worldwide localities
- Keeley mine, South Lorrain Township, Ontario, Canada
- Velardeña, and in the La Papa mine, Victoria, Hidalgo, Durango, Mexico
- Smilkov, near Votice, Czech Republic
- Bräunsdorf, Freiberg, and Schneeberg, Saxony, Germany
- Tafone, Tuscany, Italy
- Mine de la Bessade, Massiac, Haute-Loire, France
Field-hunting tip
Where it forms: In veinlets cutting gneisses containing varying amounts of graphite (Smilkov, Czech Republic). If you start seeing silver in float, you are in the right ground. Typical habit: earthy, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chapmanite?+
Where is chapmanite found?+
Is chapmanite safe to handle?+
What rocks look like chapmanite?+
What minerals are found with chapmanite?+
What kind of rock does chapmanite form in?+
What is chapmanite used for?+
Find chapmanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
