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 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: pale yellow, yellow-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.
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
- 2-3
- Density
- 2.55 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Octahedral crystals, often with cube faces
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As efflorescences formed by chemical reactions as ground water interacts with organic matter from coal and oxidizing pyrite and marcasite on a burning coal dump
Where rockhounds find ammoniomagnesiovoltaite
Classic worldwide localities
- Near Köves Hill, Pécs-Vasas, Mecsek Mountains, southern Hungary
Field-hunting tip
Where it forms: As efflorescences formed by chemical reactions as ground water interacts with organic matter from coal and oxidizing pyrite and marcasite on a burning coal dump. If you start seeing tschermigite, sabieite, kieserite in float, you are in the right ground. Typical habit: octahedral crystals, often with cube faces. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ammoniomagnesiovoltaite?+
Where is ammoniomagnesiovoltaite found?+
What rocks look like ammoniomagnesiovoltaite?+
What minerals are found with ammoniomagnesiovoltaite?+
What kind of rock does ammoniomagnesiovoltaite form in?+
What is ammoniomagnesiovoltaite used for?+
Find ammoniomagnesiovoltaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
