Novacekite in Selenite
Specimen Origin: Mina Las Animas (Santa Eulalia, Chihuahua, Mexico)
The Santa Eulalia mining district in Chihuahua is well known for its polymetallic and uranium-rich deposits, producing a wide variety of secondary minerals. At Mina Las Animas, nováčekite forms in oxidized zones where it occurs as bright yellow crystalline crusts and coatings on gypsum, especially selenite. These specimens, with vivid yellow nováčekite contrasting sharply against clear or white selenite, are valued for both their rarity and striking visual appeal.
Nováčekite in Selenite
Nováčekite is a hydrated magnesium uranyl arsenate with the formula Mg(UO₂)₂(AsO₄)₂·10–12H₂O. It belongs to the autunite group and typically appears as lemon- to straw-yellow tabular crystals or thin crusts. The mineral is strongly radioactive and often fluoresces bright yellow-green under ultraviolet light. In selenite associations, it highlights the delicate contrast between the transparent gypsum host and the vibrant secondary uranium mineral.
