Yoshiokaite is a rare hexagonal mineral belonging to the nepheline group, primarily found in volcanic ejecta blocks. It typically appears as small, colorless tabular crystals or granular aggregates and is most notably identified by its specific occurrence in sites like Miyake-jima.
Is this yoshiokaite?
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 yoshiokaite with a known reference. Yoshiokaite sits at Mohs 5-6, 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: colorless, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, granular aggregates.
Often confused with
Yoshiokaite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside yoshiokaite
Minerals reported to co-occur with yoshiokaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₁-x(Al,Si)₂O₄
- Mohs hardness
- 5-6
- Density
- 2.76-2.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Trigonal
- Crystal habit
- Tabular crystals, granular aggregates
- Cleavage
- Poor on {100}; commonly showis sets of {201} and {200} lamellae which are believed not to be related by twinning, but were probably shock-induced
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A metastable phase, as shocked crystal fragments and in devitrified glasses in a regolith breccia
Where rockhounds find yoshiokaite
Classic worldwide localities
- Moon, near the Apollo 14 landing site
Field-hunting tip
Where it forms: A metastable phase, as shocked crystal fragments and in devitrified glasses in a regolith breccia. If you start seeing anorthite, fassaite, gehlenite in float, you are in the right ground. Typical habit: tabular crystals, granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify yoshiokaite?+
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What rocks look like yoshiokaite?+
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Find yoshiokaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
