Catalog Search Guide
You can search our catalog using different mineral attributes. For example, you can search by color such as green, yellow or purple, or by chemical elements such as uranium, calcium or iron, or by mineral groups such as phosphate, silicate or carbonate. You can also filter by crystal habit like crystal, geode or crystal on matrix, by specimen size such as thumbnail, small, medium or cabinet, and by features such as radioactive or fluorescent minerals.
Autunite
Autunite is a hydrated calcium uranyl phosphate, Ca(UO2)2(PO4)2·10–12H2O, prized above all for its dazzling lemon to greenish-yellow tabular crystals and their vivid yellow-green fluorescence under both shortwave and longwave UV light. It typically forms as thin square or rectangular plates, often in fan-like sprays, foliated crusts, or serrated edge-on aggregates, with a soft hardness of 2–2.5 and a pearly to vitreous luster. As a secondary mineral, it forms in the oxidation zones of hydrothermal veins and granite pegmatites where primary uranium minerals such as uraninite have broken down, commonly alongside torbernite, meta-autunite, phosphuranylite, saléeite, uranophane, and sabugalite.
The type locality is Saint-Symphorien-de-Marmagne near Autun, in Saône-et-Loire, France, where the species was first described in 1852; nearby French classics include the Margnac mine in Haute-Vienne and the Gagnol mine at Lachaux. Exceptional specimens are also known from Bergen in Germany's Vogtland, from Sabugal and Urgeiriça in Portugal, from numerous Cornwall workings in England, and from the Daybreak Mine near Mount Spokane, Washington, one of the finest American localities. Because it readily dehydrates in air to meta-autunite, well-preserved, richly fluorescent crystal groups are genuinely scarce.
Collectors seek autunite for its striking bright green glow, elegant tabular habit, and role as a classic uranium ore mineral with roughly 48% uranium content. Fine, undamaged plates and crusts from historic French, Portuguese, German, and American localities remain among the most desirable pieces in any fluorescent mineral or uranium mineral collection.
