Aurorite is a rare manganese oxide mineral typically found as earthy or botryoidal coatings in oxidized ore deposits. It is most easily identified by its association with other manganese minerals and its specific occurrence in oxidized mine environments.
Is this aurorite?
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 aurorite with a known reference. Aurorite sits at Mohs <3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: grayish black, black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: irregular grains, platy, scaly.
Often confused with
Aurorite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Aurorite is noticeably harder (Mohs <3 vs. 1.5); streak differs, so Aurorite leaves brown, Birnessite leaves brownish-black; luster reads metallic on Aurorite and dull on Birnessite.
How to tell apart: Psilomelane is the harder of the two (Mohs 5-6 vs. <3); streak differs, so Aurorite leaves brown, Psilomelane leaves brownish black; luster reads metallic on Aurorite and submetallic on Psilomelane.
How to tell apart: Streak differs, so Aurorite leaves brown, Pyrolusite leaves black, bluish black.
Often found alongside aurorite
Minerals reported to co-occur with aurorite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnMn₃O₇·3H₂O
- Mohs hardness
- <3
- Density
- 3.8-4.1 g/cm³
- Colors
- Streak
- Brown
- Luster
- Metallic
- Transparency
- Opaque, transparent on very thin edges
- Crystal system
- Trigonal
- Crystal habit
- Irregular grains, platy, scaly
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In veinlets filling microfractures in manganoan calcite (Aurora mine, Nevada, USA)
Where rockhounds find aurorite
Classic worldwide localities
- Aurora mine, Hamilton, White Pine Co., and at Yucca Mountain, Nye Co., Nevada, USA
- Morenci, and in the Ash Peak mine, near Duncan, Greenlee Co., from the Sheep Tanks district, La Paz Co., and in the King of Arizona mine, Kofa district, Yuma Co., USA
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Kawazu mine, Shizuoka Prefecture, Japan
Field-hunting tip
Where it forms: In veinlets filling microfractures in manganoan calcite (Aurora mine, Nevada, USA). If you start seeing manganoan calcite, argentian todorokite, cryptomelane in float, you are in the right ground. Typical habit: irregular grains, platy, scaly. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify aurorite?+
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Find aurorite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
