Mikasaite is an extremely rare iron-aluminum sulfate mineral that forms in the combustion zones of coal mine fires. It typically presents as delicate, tiny tabular crystals or powdery white crusts associated with other fumarolic minerals. Due to its formation in specific high-temperature environments, collectors typically encounter it only from its type locality in Japan.
Is this mikasaite?
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 mikasaite with a known reference. Mikasaite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Mikasaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Mikasaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, yellowish-white, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, incrustations.
Often confused with
Mikasaite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside mikasaite
Minerals reported to co-occur with mikasaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Fe³⁺,Al)₂(SO₄)₃
- Mohs hardness
- 2
- Density
- 2.85 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Tabular Crystals, Incrustations
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Burning Coal Mine Dump
- Typical price
- $50-300 per specimen
Where rockhounds find mikasaite
Classic worldwide localities
- Mikasa coal mine, Hokkaido, Japan
Field-hunting tip
Look in burning coal mine dump country — that is the host setting where mikasaite typically forms. If you start seeing sulphur, alunogen, halotrichite in float, you are in the right ground. Field specimens usually show a tabular crystals, incrustations habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find mikasaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
