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, so Grimselite leaves white, Liebigite leaves pale yellow.
How to tell apart: Streak differs, so 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, 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.
