Ammoniomagnesiovoltaite is a very rare sulfate mineral in the voltaite group, typically found as small, dark octahedral crystals. It forms primarily in the oxidized zones of mining environments where ammonium-rich solutions interact with magnesium and iron sulfides.
Is this ammoniomagnesiovoltaite?
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 ammoniomagnesiovoltaite with a known reference. Ammoniomagnesiovoltaite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ammoniomagnesiovoltaite leaves a yellowish-green streak.
- 3Read the lusterHold the specimen under a strong light. Ammoniomagnesiovoltaite typically shows a vitreous 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 with cube faces.
Often confused with
Ammoniomagnesiovoltaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ammoniomagnesiovoltaite leaves yellowish-green, Voltaite leaves greenish gray; luster reads vitreous on Ammoniomagnesiovoltaite and resinous on Voltaite.
How to tell apart: Streak differs, so Ammoniomagnesiovoltaite leaves yellowish-green, Pickeringite leaves white; luster reads vitreous on Ammoniomagnesiovoltaite and silky on Pickeringite.
Often found alongside ammoniomagnesiovoltaite
Minerals reported to co-occur with ammoniomagnesiovoltaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Mg₅Fe³⁺₃Al(SO₄)₁₂·18H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.14-2.18 g/cm³
- Colors
- Streak
- Yellowish-green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals, Often with Cube Faces
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Sulfide-rich Ore Deposits, Coal Mine Dumps
- Typical price
- $20-150 for rare specimen fragments
Where rockhounds find ammoniomagnesiovoltaite
Classic worldwide localities
- United Verde Mine, Arizona, USA
- Coal mines, Czech Republic
- Various volcanic fumaroles
Field-hunting tip
Look in oxidized zones of sulfide-rich ore deposits, coal mine dumps country, the host setting where ammoniomagnesiovoltaite typically forms. If you start seeing gypsum, alunogen, jarosite in float, you are in the right ground. Field specimens usually show a octahedral crystals, often with cube faces habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ammoniomagnesiovoltaite?+
Where is ammoniomagnesiovoltaite found?+
How much is ammoniomagnesiovoltaite worth?+
What rocks look like ammoniomagnesiovoltaite?+
What minerals are found with ammoniomagnesiovoltaite?+
What kind of rock does ammoniomagnesiovoltaite form in?+
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Find ammoniomagnesiovoltaite on the map
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