Hetaerolite is a zinc manganese oxide often found as black, shiny botryoidal masses. It is most famous for its occurrences in the unique zinc-manganese deposits at Franklin and Sterling Hill, New Jersey, where it typically forms as a secondary alteration product.
Is this hetaerolite?
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 hetaerolite with a known reference. Hetaerolite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic to submetallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: botryoidal, massive, stalactitic.
Often confused with
Hetaerolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads metallic to submetallic on Hetaerolite and submetallic on Hausmannite.
How to tell apart: Streak differs, so Hetaerolite leaves dark brown, Psilomelane leaves brownish black; luster reads metallic to submetallic on Hetaerolite and submetallic on Psilomelane.
Often found alongside hetaerolite
Minerals reported to co-occur with hetaerolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ZnMn₂O₄
- Mohs hardness
- 6
- Density
- 5.18 g/cm³
- Colors
- Streak
- Dark brown
- Luster
- Metallic to submetallic
- Transparency
- Opaque, transparent through thin edges
- Crystal system
- Tetragonal
- Crystal habit
- Botryoidal, massive, stalactitic
- Cleavage
- {001}, indistinct; two additional, probably on {112} and {011}
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- A secondary mineral associated with other manganese minerals, primarily in hydrothermal ore deposits
Where rockhounds find hetaerolite
Classic worldwide localities
- Sterling Hill, Ogdensburg, and Franklin, Sussex Co., New Jersey, USA
- Cochise Co., at the Lucky Cuss mine, Tombstone, and the Campbell and Junction mines, Bisbee, Arizona, USA
- Domeroy property, Pioneer district, Pinal Co., Arizona, USA
- Contact mine, Grant Co., New Mexico, USA
- Rodna, Romania
- Moresnet, Belgium
Field-hunting tip
Where it forms: A secondary mineral associated with other manganese minerals, primarily in hydrothermal ore deposits. If you start seeing franklinite, chalcophanite, hodgkinsonite in float, you are in the right ground. Typical habit: botryoidal, massive, stalactitic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find hetaerolite on the map
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