Tschermigite is a rare ammonium aluminum sulfate that typically forms as a white efflorescent crust or small octahedral crystals near burning coal seams. It is highly soluble in water and must be kept in a cool, dry environment to prevent dehydration and breakdown of the specimen.
Is this tschermigite?
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 tschermigite with a known reference. Tschermigite sits at Mohs 1.5, 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, silky if fibrous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, deliquescent, fibrous.
Often confused with
Tschermigite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside tschermigite
Minerals reported to co-occur with tschermigite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)Al(SO₄)₂·12H₂O
- Mohs hardness
- 1.5
- Density
- 1.645 g/cm³
- Streak
- White
- Luster
- Vitreous, silky if fibrous
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Crystalline, deliquescent, fibrous
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An uncommon secondary mineral in lignite and brown coal deposits and bituminous shales and on burning coal seams or waste heaps; as efflorescences around solfataras or geothermal gas vents and fumaroles
Where rockhounds find tschermigite
1 mapped spotsClassic worldwide localities
- Burning coal waste piles at Glen Lyon, Luzerne Co., and Williamstown, Dauphin Co., Pennsylvania, USA
- Geysers, Sonoma Co., and at Sulfur Bank, Lake Co., California, USA
- Wamsutter, Sweetwater Co., Wyoming, USA
- Čermníky (Tschermig), east of Kaaden, at Libušín, near Kladno, Zastávka, near Brno, in the brown coal basins near Most and Bílina, Czech Republic
- Voinesti, Romania
- Magyarórosbánya, Hungary
Field-hunting tip
Where it forms: An uncommon secondary mineral in lignite and brown coal deposits and bituminous shales and on burning coal seams or waste heaps; as efflorescences around solfataras or geothermal gas vents and fumaroles. If you start seeing gypsum, ammoniojarosite, epsomite in float, you are in the right ground. Typical habit: crystalline, deliquescent, fibrous. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wyoming. Start trip planning there.
Common questions
How do you identify tschermigite?+
Where is tschermigite found?+
Can I find tschermigite in the United States?+
What rocks look like tschermigite?+
What minerals are found with tschermigite?+
What kind of rock does tschermigite form in?+
What is tschermigite used for?+
Find tschermigite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
