Elemental Composition (by mass)
| Element | Mass % | Visual |
|---|---|---|
| U Uranium | 61.33% | |
| O Oxygen | 22.67% | |
| P Phosphorus | 7.98% | |
| Ca Calcium | 5.16% | |
| H Hydrogen | 2.86% |
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
⏳ Long-term Aging & Care Timeline
dehydrationyears
Trigger: low humidity
Intervention: Hydrated U phosphate loses water → meta-autunite. Loses some yellow-green color. Sealed humid case slows.
Pronunciation
/ˈɔːtənaɪt/
↔ AW-tuh-nite
from Autun, France
⚠ Safety & Handling
☢radioactiveextreme
Hydrated uranyl phosphate — emits alpha and beta radiation plus gamma from daughter isotopes.
Handling: Store in lead-lined or dedicated radioactive cabinet. Never handle barehanded. Avoid prolonged proximity. Wash hands after exposure. Dispose properly.
Information provided in good faith. Consult local hazmat regulations for transport and disposal. Severely hazardous specimens may require special storage cabinets.
UV Fluorescence
SW (254 nm)
Yellow-green
very strong
LW (365 nm)
Yellow-green
strong
Uranium phosphate; brilliant yellow-green SW. Uranium-related fluorescence.
SW = shortwave (germicidal lamp). LW = longwave (blacklight). Response varies with locality, trace impurities, and treatment.
Luster
vitreous→pearly
Plates show pearly luster on cleavage.
Diagnostic Field Tests
UV test→ Brilliant yellow-green fluorescence
Uranium mineral — handle with caution.
⚠ Use dilute HCl (~10%) only on inconspicuous spots; rinse promptly. Smell-tests should be brief and ventilated. Taste-test ONLY halite/sylvite — never lead, arsenic, or sulfur minerals.
Care notesHandle with gloves; radioactive. Store in vented box. Full cleaning guide →
Market availability: Very rare
Auction-tier rarity. Often single-locality or specimen-grade only.
Collector tier: Micromount / Niche
Best appreciated at thumbnail or smaller scale — often dull-colored, sub-millimeter, or radioactive. Specialist appeal.
Mohs 2–2.5
Vickers (~) 75 HV
Knoop (~) 85 HK
Geological setting
Plutonic igneousPegmatite
Diagnostic properties
Radioactive
Optical Effects
Fluorescent
Mohs Hardness
2–2.5
Autunite sits at 2–2.5 on the Mohs scale — soft enough to be scratched by a fingernail.
Colors:
Streak
Yellow
Yellow
Crystal system
Tetragonal
Tetragonal
PhosphatesPhosphates (Uranyl)
TL;DR · 1 min read
Autunite (Ca(UO₂)₂(PO₄)₂·10–12H₂O) is a hydrous calcium uranyl phosphate forming brilliant fluorescent yellow-green tabular crystals — among the most strikingly colored uranium minerals. Named after Autun (France), it forms in oxidized cap zones of uranium-bearing pegmatites and granites.
Autunite (Ca(UO₂)₂(PO₄)₂·10–12H₂O) is a hydrous calcium uranyl phosphate forming brilliant fluorescent yellow-green tabular crystals — among the most strikingly colored uranium minerals. Named after Autun (France), it forms in oxidized cap zones of uranium-bearing pegmatites and granites. Highly radioactive — collector specimens require shielded storage.