Paramarkeyite
Chemical formula: Ca₂(U⁶⁺O₂)(CO₃)₃(H₂O)₅
Paramarkeyite is a rare, secondary uranyl mineral that forms bright yellow, acicular crystals and is prized by collectors of radioactive minerals.
Properties
- Mohs hardness
- 2.5
- Color
- Pale green-yellow
- Luster
- Vitreous
- Streak
- White
- Density
- 2.91
- Cleavage
- On {100}; also probable two good cleavages, on {010} and {001}.
- Fracture
- Irregular/Uneven
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Paramarkeyite can be identified by its characteristic appearance: it forms bright yellow, acicular or hair-like crystals gathered in radial aggregates. A key diagnostic feature is its very strong, bright green fluorescence under UV light. Measuring radioactivity with a Geiger counter will immediately confirm the presence of uranium. ## Distinguishing from Similar Minerals Paramarkeyite is visually almost identical to markeyite. Distinguishing these two minerals is impossible without advanced laboratory analyses, such as X-ray diffraction (XRD). It can also be confused with other secondary uranyl minerals of similar appearance, such as uranophane or gipsite, but the characteristic aggregate form and intense fluorescence are strong indicators. ## Crystal Forms The mineral forms elongated, acicular crystals with a nearly rectangular cross-section. These crystals almost always occur as radial or stellate aggregates, as well as felted, fibrous masses and coatings.
Geological environment
## Genesis Paramarkeyite is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of carbonate-rich waters acting on primary uranium minerals, such as uraninite. It crystallizes under low-temperature conditions, forming as efflorescences and coatings on mine workings walls, and in fissures of sedimentary rocks (mainly sandstones and limestones). ## Mineral Associations It most commonly co-occurs with markeyite, to which it is directly related. Other associated minerals include gypsum, uraninite, and other secondary uranyl minerals such as schröckingerite, andersonite, and liebigite. ## Localities The most important and type locality for paramarkeyite is the Markey Mine in Red Canyon, San Juan County, Utah, USA. This is currently the only confirmed and well-documented locality for this mineral worldwide.
Rarity
Very rare
For collectors
## Quality Criteria The most prized paramarkeyite specimens are those with well-formed, rich aggregates of acicular crystals of an intense yellow color. The size and aesthetics of rosettes or radial clusters are important. Contrast with a dark matrix significantly enhances visual appeal and specimen value. Purity (lack of damage to delicate crystals) is a key factor. ## Popular Localities The only source of collector specimens is the historical type locality – the Markey Mine in Utah, USA. All specimens available on the market originate from this single location.
Care and storage
## Cleaning Paramarkeyite specimens are generally not cleaned due to their extreme delicacy. Any attempt at mechanical cleaning, even with a soft brush, risks destroying the fragile crystals. If absolutely necessary, compressed air can be used from a distance to remove loose dust particles. ## What to Avoid Avoid contact with water and chemicals, which can damage or dissolve the mineral. The crystals are very brittle, so avoid shocks, vibrations, and touching. As a highly radioactive mineral, it requires special precautions – avoid inhaling dust and direct, prolonged skin contact. ## Storage Specimens should be stored in sealed, transparent containers (such as "perky boxes") that protect them from mechanical damage and dust, and also limit radon dispersion. Store away from areas of permanent human occupancy, in a well-ventilated room. It should be kept away from radiation-sensitive materials (e.g., photographic film).