Ammoniovoltaite is a rare sulfate mineral found primarily in fumarolic or post-mining environments where ammonium-rich solutions interact with iron-sulfide oxidation products. Collectors should look for dark, well-formed octahedral crystals typically found encrusting mine walls or localized in coal-bearing strata. It is highly soluble in water and should be kept in a dry, sealed environment to prevent degradation.
Is this ammoniovoltaite?
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 ammoniovoltaite with a known reference. Ammoniovoltaite 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. Ammoniovoltaite leaves a greenish-white streak.
- 3Read the lusterHold the specimen under a strong light. Ammoniovoltaite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals.
Often confused with
Ammoniovoltaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ammoniovoltaite leaves greenish-white, Voltaite leaves greenish gray.
How to tell apart: Ammoniovoltaite is noticeably harder (Mohs 3 vs. 1.5-2); streak differs — Ammoniovoltaite leaves greenish-white, Pickeringite leaves white; luster reads resinous on Ammoniovoltaite and silky on Pickeringite.
Often found alongside ammoniovoltaite
Minerals reported to co-occur with ammoniovoltaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Fe₅Fe₃Al(SO₄)₁₂·18H₂O
- Mohs hardness
- 3
- Density
- 2.68 g/cm³
- Colors
- Streak
- Greenish-white
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Post-mine Fumarole Deposits and Coal Fire Oxidation Zones
- Typical price
- $50-300 per specimen
Where rockhounds find ammoniovoltaite
Classic worldwide localities
- United Verde mine, Arizona, USA
- Alum Cave Bluff, Tennessee, USA
- Klodzko, Poland
Field-hunting tip
Look in post-mine fumarole deposits and coal fire oxidation zones country — that is the host setting where ammoniovoltaite typically forms. If you start seeing jarosite, gypsum, alunogen in float, you are in the right ground. Field specimens usually show a octahedral crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ammoniovoltaite?+
Where is ammoniovoltaite found?+
How much is ammoniovoltaite worth?+
What rocks look like ammoniovoltaite?+
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Find ammoniovoltaite on the map
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