Yugawaralite is a relatively rare calcium-rich zeolite often found as distinctive white to colorless bladed or tabular crystals. It typically forms in cavities within volcanic rocks and is prized by collectors for its attractive, often radiating crystal aggregates. First discovered near Yugawara Hot Springs in Japan, it is now found in various volcanic regions globally.
Is this yugawaralite?
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 yugawaralite with a known reference. Yugawaralite sits at Mohs 4.5-5, 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 to pearly, iridescent on {010}.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, bladed, radiating sprays.
Often confused with
Yugawaralite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside yugawaralite
Minerals reported to co-occur with yugawaralite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₂Si₆O₁₆·4H₂O
- Mohs hardness
- 4.5-5
- Density
- 2.20-2.23 g/cm³
- Streak
- White
- Luster
- Vitreous to pearly, iridescent on {010}
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, bladed, radiating sprays
- Cleavage
- {401}, {100} distinct, {101} imperfect; parting on {010}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- As crystals lining cavities, and veinlets, typically deposited in active geothermal areas
Where rockhounds find yugawaralite
Classic worldwide localities
- Yellowstone National Park, Wyoming, and the Chena Hot Springs area, about 65 km east of Fairbanks, Alaska, USA
- Yugawara Hot Spring, Kanagawa Prefecture, Japan
- Shimoda, and in the Toi and Seikoshi mines, Shizuoka Prefecture, Japan
- Takinoue, Kakkonda Hot Springs, Iwate Prefecture, Japan
- Khandivali and Malad quarries, near Bombay, Maharashtra, India
- Heinabergsjökull and Hvalsgod (Klif), Hvalfjord, Iceland
Field-hunting tip
Where it forms: As crystals lining cavities, and veinlets, typically deposited in active geothermal areas. If you start seeing zeolites, gyrolite, okenite in float, you are in the right ground. Typical habit: tabular crystals, bladed, radiating sprays. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify yugawaralite?+
Where is yugawaralite found?+
What rocks look like yugawaralite?+
What minerals are found with yugawaralite?+
What kind of rock does yugawaralite form in?+
What is yugawaralite used for?+
Find yugawaralite on the map
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