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. Hetaerolite leaves a dark brown streak.
- 3Read the lusterHold the specimen under a strong light. Hetaerolite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: botryoidal, massive, or stalactitic crusts.
Often confused with
Hetaerolite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Hetaerolite leaves dark brown, Hausmannite leaves brownish-red.
How to tell apart: Streak differs — Hetaerolite leaves dark brown, Romanèchite leaves shiny brownish black; luster reads submetallic on Hetaerolite and submetallic to dull on Romanèchite.
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
- 4.85-4.90 g/cm³
- Colors
- Streak
- Dark Brown
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Botryoidal, Massive, Or Stalactitic Crusts
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphic Zinc-manganese Ore Bodies
- Typical price
- $20-150 per specimen depending on quality and origin
Where rockhounds find hetaerolite
Classic worldwide localities
- Sterling Hill Mine, New Jersey, USA
- Franklin, New Jersey, USA
- Tsumeb Mine, Namibia
- Långban, Sweden
Field-hunting tip
Look in metamorphic zinc-manganese ore bodies country — that is the host setting where hetaerolite typically forms. If you start seeing franklinite, willemite, zincite in float, you are in the right ground. Field specimens usually show a botryoidal, massive, or stalactitic crusts habit, so 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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