Chalcophanite is a manganese oxide mineral typically found as small, shiny, metallic black tabular crystals or delicate rosettes. It is most famous for occurring in the oxidized zones of the Franklin and Sterling Hill zinc deposits, where it often forms as a secondary coating on other manganese minerals.
Is this chalcophanite?
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 chalcophanite with a known reference. Chalcophanite 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: chocolate-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic to submetallic.
- 4Match the color rangeCompare against the expected color range: black, blue, bluish black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: foliated, stalactitic.
Often confused with
Chalcophanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Hausmannite is the harder of the two (Mohs 5.5 vs. 2.5); streak differs, so Chalcophanite leaves chocolate-brown, Hausmannite leaves dark reddish brown; luster reads metallic to submetallic on Chalcophanite and submetallic on Hausmannite.
How to tell apart: Psilomelane is the harder of the two (Mohs 5-6 vs. 2.5); streak differs, so Chalcophanite leaves chocolate-brown, Psilomelane leaves brownish black; luster reads metallic to submetallic on Chalcophanite and submetallic on Psilomelane.
How to tell apart: Chalcophanite is noticeably harder (Mohs 2.5 vs. 1.5); streak differs, so Chalcophanite leaves chocolate-brown, Birnessite leaves brownish-black; luster reads metallic to submetallic on Chalcophanite and dull on Birnessite.
Often found alongside chalcophanite
Minerals reported to co-occur with chalcophanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ZnMn₃O₇·3H₂O
- Mohs hardness
- 2.5
- Density
- 3.91 g/cm³
- Colors
- Streak
- Chocolate-brown
- Luster
- Metallic to submetallic
- Transparency
- Opaque, transparent on very thin edges
- Crystal system
- Trigonal
- Crystal habit
- Foliated, stalactitic
- Cleavage
- Perfect on {0001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A common component of the weathered zones above zinc- and manganese-bearing base- metal deposits
Where rockhounds find chalcophanite
Classic worldwide localities
- Sterling Hill, Ogdensburg, and Franklin, Sussex Co., New Jersey, USA
- Price mine, near Newport, Giles Co., Virginia, USA
- Philipsburg district, Granite Co., Montana, USA
- Wolftone mine, Leadville, Lake Co., Colorado, USA
- Ojuela mine, Mapimi, Durango, Mexico
- Broken Hill, New South Wales, Australia
Field-hunting tip
Where it forms: A common component of the weathered zones above zinc- and manganese-bearing base- metal deposits. If you start seeing cryptomelane, manganite, hetaerolite in float, you are in the right ground. Typical habit: foliated, stalactitic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find chalcophanite on the map
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