Larisaite is a rare uranyl selenite mineral typically found as small yellow, tabular crystals or platy aggregates. It is highly sought after by collectors of radioactive mineral species due to its scarcity and distinct chemistry, and it is almost exclusively known from the Repete mine in Utah.
Is this larisaite?
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 larisaite with a known reference. Larisaite 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. Larisaite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Larisaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, platy aggregates.
Often confused with
Larisaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Marthozite is the harder of the two (Mohs 3 vs. 2); streak differs — Larisaite leaves yellow, Marthozite leaves pale yellow.
How to tell apart: Streak differs — Larisaite leaves yellow, Derriksite leaves pale green; luster reads vitreous on Larisaite and adamantine on Derriksite.
Often found alongside larisaite
Minerals reported to co-occur with larisaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na(H₃O)(UO₂)₃(SeO₃)₂O₂·4H₂O
- Mohs hardness
- 2
- Density
- 3.37 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Platy Aggregates
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Uranium-bearing Sandstone Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find larisaite
Classic worldwide localities
- Repete mine, San Juan County, Utah, USA
Field-hunting tip
Look in oxidized uranium-bearing sandstone deposits country — that is the host setting where larisaite typically forms. If you start seeing uranyl selenites, gypsum, quartz in float, you are in the right ground. Field specimens usually show a tabular crystals, platy aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find larisaite on the map
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