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. Chalcophanite leaves a chocolate brown streak.
- 3Read the lusterHold the specimen under a strong light. Chalcophanite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black, bluish-black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, rosettes, botryoidal, crusts.
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 5-5.5 vs. 2.5); streak differs — Chalcophanite leaves chocolate brown, Hausmannite leaves brownish-red; luster reads metallic on Chalcophanite and submetallic on Hausmannite.
How to tell apart: Romanèchite is the harder of the two (Mohs 5-6 vs. 2.5); streak differs — Chalcophanite leaves chocolate brown, Romanèchite leaves shiny brownish black; luster reads metallic on Chalcophanite and submetallic to dull on Romanèchite.
How to tell apart: Chalcophanite is noticeably harder (Mohs 2.5 vs. 1.5); streak differs — Chalcophanite leaves chocolate brown, Birnessite leaves brownish-black; luster reads metallic 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
- (Zn,Fe²⁺,Mn²⁺)Mn⁴⁺₃O₇·3H₂O
- Mohs hardness
- 2.5
- Density
- 3.9 g/cm³
- Colors
- Streak
- Chocolate Brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Tabular Crystals, Rosettes, Botryoidal, Crusts
- Cleavage
- Perfect Basal
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Oxidized Zones of Zinc-manganese Ore Deposits
- Typical price
- $15-150 depending on specimen size and quality
Where rockhounds find chalcophanite
Classic worldwide localities
- Franklin, New Jersey
- Sterling Hill, New Jersey
- Mistra, Greece
- N'Chwaning Mine, South Africa
Field-hunting tip
Look in oxidized zones of zinc-manganese ore deposits country — that is the host setting where chalcophanite typically forms. If you start seeing franklinite, willemite, zincite in float, you are in the right ground. Field specimens usually show a tabular crystals, rosettes, botryoidal, crusts habit, so 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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