phosphates
Autunite
Ca(UO2)2(PO4)2·10-12H2O
- Also known as
- calcium uranite
- Crystal system
- orthorhombic
- Hardness
- 2–2.5 on the Mohs scale
- Lustre
- pearly
- Colour
- Lemon yellow to yellow-green
- Where it forms
- By oxidation of uranium minerals near the surface, as flat platy crystals.
- Chiefly from
- Autun, FranceWashington, United StatesPortugalDemocratic Republic of the Congo
Why it is that colour
The uranyl ion. It is also intensely fluorescent, glowing bright green under ultraviolet light.
Safety
Radioactive. Autunite contains uranium and its decay products, it emits alpha, beta and gamma radiation, and it produces radon gas. The primary hazard is not the external dose from a small specimen but inhalation and ingestion: it is soft, it flakes, and it dehydrates into a powder called meta-autunite that sheds readily. It should be kept sealed, in a ventilated place, away from living areas and away from children, and never handled with bare hands or brought near food. It is sold to collectors online, routinely.
Where it comes from
Specimen material chiefly from the United States, Portugal and France. Uranium mining has left a serious contamination legacy in several places, including Navajo Nation lands in the American Southwest where hundreds of abandoned mines are still being remediated.
Historical use
Named after Autun in France. A minor uranium ore, and a standard prospecting indicator because its fluorescence makes it findable with an ultraviolet lamp at night.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
Worth knowing
Radioactive minerals are freely sold to collectors, and the collecting community has well-established norms about them — sealed containers, ventilation, no bare-handed handling, kept away from bedrooms. Those norms exist because the hazard is real and manageable rather than because it is catastrophic.
Autunite is in this collection because those norms do not travel with the specimen into the wellbeing market, where a bright yellow-green mineral that glows under UV is an obvious candidate for a shelf. Anything sold as a uranium mineral, and anything unexpectedly fluorescing bright green, warrants checking before it goes anywhere near a bedside table.
Identity checked against IMA-CNMNC master list, June 2025.