Uraninita
Uraninita is a mineral with formula UO₂, in the Óxidos group. This specimen comes from Joachimsthal, Jáchymov, Karlovy Vary, Bohemia, República Checa and joined the Terrium collection in 1898.
Description
Massive, heavy fragment with a dark, compact-looking core and black to blackish-brown zones attributable to altered uraninite. The surface shows irregular, earthy yellow, ochre and greenish coatings, with scattered apple-green areas and brownish-yellow crusts. Reaches 550 μSv/h.
History of this specimen
The piece retains two old labels. The first documented owner of this historic piece was Marquis Adrien Charles de Mauroy (1848–1927), a French mining engineer, agronomist and mineralogist, who graduated in 1872 as top of his class at the École des Mines de Paris. He assembled one of the most notable private meteorite collections of his time and, in the early twentieth century, donated more than 1,000 pieces to the Vatican Observatory. On his handwritten label he noted the synonyms of the day: besides "Uranochalcite" for the apple-green phase ("vert pomme"), he writes "Zippeite / Uraconise" as equivalent names for the yellow phase, and "Gummite / Eliasite" for the brownish-yellow phase. The second label is a commercial label, also penned in ink, from Maison Deyrolle, Paris—a celebrated cabinet-of-curiosities shop founded in 1835 and specialised in taxidermy, entomology and natural science objects. I cannot say whether it first formed part of Marquis Adrien Charles de Mauroy’s collection and then passed through Deyrolle, or the other way round. Either way, it is a textbook transitional piece: it marks the shift from the aristocratic cabinet of curiosities, collecting for curiosity and extravagance, to minerals ordered by a scientific gaze aiming to understand and classify matter—a transformation taking shape for barely a century with institutions such as the École des Mines de Paris and the Bergakademie Freiberg. It also belongs to the historical moment of the discovery of radioactivity (1898), years when the Curie couple were crushing uranium minerals like this to understand what those rays were and which elements emitted them.
About Uraninita
Although the dealer identified it as liebigite without XRD and the historical labels cite "Uranochalcite vert pomme", no micaceous crystals or visual features sufficient to confirm autunite or liebigite are seen with the naked eye. In addition, the label affixed to the piece already identifies it as "Pesblende" [sic]. The more cautious reading is therefore to catalogue it as uraninite: the primary mineral core and the source of the secondary alterations described on the label. The documentation also preserves the historical reading of those secondaries: "Zippeite / Uraconise" for the yellow phase, "Gummite / Eliasite" for the brownish-yellow phase, and "Uranochalcite" for the apple-green phase. The piece reaches 550 μSv/h, a high activity for a collection specimen, consistent with a primary uraninite mass and not with a mere superficial green secondary.
About the locality
Old Joachimsthal, now Jáchymov, was one of the most important mining districts of Bohemia and a key place in the history of uranium minerals. Its veins yielded uraninite, a wide variety of secondary minerals, and several historical names linked to alteration of the primary mineral. In old pieces, Joachimsthal labels carry special documentary weight because they connect directly with classic Central European mining, historical nomenclature and the mineral trade of the 19th and 20th centuries.
Technical data
- Catalogue No.
- 0641
- Composition
- UO₂
- Name
- Uraninita
- Group
- Óxidos
- Category
- Núcleus Ardens
- Matrix
- Uraninita masiva
- Associations
- zippeite, uraninita, gumita, eliasita
- Mine
- Joachimsthal
- District / Municipality
- Jáchymov
- Province
- Karlovy Vary
- Region
- Bohemia
- Country
- República Checa
- Size (cm)
- 6 × 4.5 × 2
- Weight
- 100 g
- Acquired
- 1898
- Ex-collection
- Marquis Adrien Charles de Mauroy ↔ DEYROLLE
- Etymology
- From the element uranium, named by Klaproth in honour of the planet Uranus.
- Quality
- Top
- Value trend
- Estable
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