Atencioite
Chemical formula: Ca<sub>2</sub>Fe<sup>2+</sup><sub>3</sub>Mg<sub>2</sub>Be<sub>4</sub>(PO<sub>4</sub>)<sub>6</sub>(OH)<sub>4</sub>·6H<sub>2</sub>O
Atencioite is a very rare phosphate mineral, forming spherical aggregates of green, tabular crystals, discovered in Brazil.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- Light green
- Density
- 2.86
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification A characteristic feature of atencioite is its small, spherical aggregates with a radial structure, composed of fine, tabular crystals of green or bluish-green color. Its occurrence in association with other rare phosphates in granite pegmatites is a key indicator. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). ## Distinguishing from Similar Minerals Atencioite can be confused with other secondary phosphates forming spherical aggregates, such as wavellite, turquoise, or wardite. It is usually distinguished from wavellite by its more bluish hue and mineral association. Turquoise is harder and rarely forms such well-defined spherical aggregates with a radial internal structure. Wardite has a similar appearance but a different chemical composition and often occurs in different parageneses. Certain differentiation is possible almost exclusively by laboratory methods. ## Crystal Forms Atencioite crystals are tabular or lamellar, flattened parallel to {001}. They intergrow into radial, spherical, or hemispherical aggregates.
Geological environment
## Genesis Atencioite is a secondary phosphate mineral. It forms as a result of hydrothermal processes in the late stage of crystallization of complex granite pegmatites, rich in phosphorus and beryllium. It forms in rock cavities and fissures as a result of the alteration of earlier phosphate minerals, such as beryllonite. ## Mineral Associations This mineral co-occurs with other phosphates at its discovery site. The most important associated minerals include: wardite, eosphorite, zanazziite, moraesite, beryllonite, apatite, as well as quartz, muscovite, and albite. ## Localities The only confirmed and described locality for atencioite in the world is its type locality - the Sapucaia mine (Proberil), located in Sapucaia do Norte, in the municipality of Galiléia, in Minas Gerais state, Brazil.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of atencioite specimens is assessed based on the size and development of the spherical aggregates. Specimens with distinct, undamaged spheres of intense, bluish-green color are most valued. The contrast with the rock matrix and the presence of rare associated minerals, which enhance the scientific and aesthetic value of the specimen, are also important. Due to the microscopic nature of the mineral, all specimens are considered "micromounts". ## Popular Localities The only source of atencioite specimens is the Sapucaia mine in Minas Gerais, Brazil. Material from this locality is extremely rare and sought after by specialized collectors of rare minerals and "micromounts".
Care and storage
## Cleaning Atencioite specimens are extremely delicate and small. Mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water is not recommended due to the risk of damaging delicate aggregates and potential reactivity. ## What to Avoid Contact with chemicals, especially acids, which can destroy the mineral, must be strictly avoided. It should be protected from ultrasound, high temperatures, shocks, and impacts. Brittle aggregates can easily disintegrate. ## Storage It is recommended to store specimens in sealed, padded "micromount" boxes to protect them from dust, moisture, and mechanical damage. Display should be in enclosed showcases, away from direct sunlight and sources of vibration.