Astrocyanite-(Ce)
Chemical formula: Cu<sup>2+</sup><sub>2</sub>Ce<sup>3+</sup><sub>2</sub>(U<sup>6+</sup>O<sub>2</sub>)(CO<sub>3</sub>)<sub>5</sub>(OH)<sub>2</sub>·1.5H<sub>2</sub>O
Astrocyanite-(Ce) is a very rare copper, cerium, and uranium mineral, forming characteristic blue aggregates in rosette shapes.
Properties
- Mohs hardness
- 2-3
- Luster
- Vitreous
- Streak
- Light blue
- Density
- 4.11
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Astrocyanite-(Ce) is relatively easy to identify visually due to its characteristic appearance: intensely blue, spherical or star-like aggregates on the matrix rock. It reacts with hydrochloric acid, dissolving rapidly. It is a secondary mineral, occurring in the oxidation zones of uranium-copper deposits. ## Distinguishing from similar minerals It can be confused with other blue secondary copper minerals, such as azurite, but its star-like aggregates are unique. From similar-looking minerals of the microlite group (e.g., uranomicrolite), it is distinguished by its reaction with acid. In rare cases, it may resemble blue aggregates of boltwoodite, but astrocyanite has a much more intense color. ## Crystal forms It forms very small, thin, tabular crystals with a hexagonal outline. These crystals almost always occur in radial, spherical, or star-like aggregates, reaching up to 1 mm in diameter.
Geological environment
## Genesis Astrocyanite-(Ce) is a secondary mineral, forming in the oxidation zones of hydrothermal uranium-copper-cobalt deposits. It crystallizes in vugs and fissures of sedimentary rocks (mainly dolomites and shales), as a result of the weathering of primary uranium and copper ores in the presence of solutions rich in carbonates and rare earth elements. ## Mineral associations It co-occurs with other secondary uranium and copper minerals, such as uranophane, kamotoite-(Y), schuilingite-(Nd), françoisite-(Nd), masuyite, cuprosklodowskite, as well as with dolomite and quartz. ## Localities The most important and type locality for astrocyanite-(Ce) is the Kamoto East mine in the Kolwezi district, Lualaba province, Democratic Republic of Congo. This is the only confirmed locality from which well-formed specimens of this mineral originate.
Rarity
Very rare
For collectors
## Quality criteria The most prized astrocyanite-(Ce) specimens are those on which numerous, well-formed, isolated aggregates of intense blue color are visible, contrasting with a light matrix rock (most often white or pink dolomite). The size of the aggregates is crucial – specimens with rosettes exceeding 1 mm in diameter are exceptionally rare and sought after. The absence of damage to the delicate, acicular crystals is also important. ## Popular localities The only source of collectible specimens is the historical find in the Kamoto East mine in the Democratic Republic of Congo. The mineral is not currently being extracted, and all specimens available on the market come from old collections.
Care and storage
## Cleaning Astrocyanite-(Ce) specimens are extremely delicate and brittle. Mechanical or chemical cleaning is not recommended. If necessary, dust can be very carefully removed with a soft brush or a photographic air blower. Avoid contact with water, which can damage the mineral. ## What to avoid The mineral is sensitive to acids, which cause it to dissolve rapidly with the release of carbon dioxide. Avoid vibrations, impacts, and contact with chemicals. As a uranium mineral, it is radioactive and requires careful handling – avoid inhaling dust and wash hands after each contact. ## Storage It is recommended to store specimens in sealed, padded containers (e.g., "micromount" boxes) to protect them from mechanical damage and dust. It should be stored away from other minerals that could be damaged by radiation. Display should be in a closed cabinet, away from direct sunlight and heat sources.