Grimselite is a rare uranyl carbonate mineral typically found as small, bright yellow to yellow-green tabular crystals. It is most famous from its type locality at the Grimsel Pass in Switzerland, where it occurs as a secondary mineral on granite surfaces. Collectors value it for its vibrant appearance and strong fluorescence under ultraviolet light.
Is this grimselite?
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 grimselite with a known reference. Grimselite 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. Grimselite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Grimselite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-green.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: tabular crystals, crusts, or coatings.
Often confused with
Grimselite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Grimselite leaves white, Liebigite leaves pale yellow.
How to tell apart: Streak differs — Grimselite leaves white, Schröckingerite leaves pale yellow; luster reads vitreous on Grimselite and pearly on Schröckingerite.
Often found alongside grimselite
Minerals reported to co-occur with grimselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₃Na(UO₂)₂(CO₃)₃·6H₂O
- Mohs hardness
- 2
- Density
- 3.37 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular Crystals, Crusts, Or Coatings
- Cleavage
- Good
- Fluorescence
- Bright Green Under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Granite
- Typical price
- $50-300 per specimen
Where rockhounds find grimselite
Classic worldwide localities
- Grimsel Pass, Switzerland
- Schwarzwald, Germany
Field-hunting tip
Look in hydrothermal veins in granite country — that is the host setting where grimselite typically forms. If you start seeing fluorite, quartz, uraninite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, or coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify grimselite?+
Where is grimselite found?+
How much is grimselite worth?+
Is grimselite safe to handle?+
What rocks look like grimselite?+
What minerals are found with grimselite?+
What kind of rock does grimselite form in?+
What is grimselite used for?+
Find grimselite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
