Burangaite
Chemical formula: NaFe²⁺Al₅(PO₄)₄(OH)₆·2H₂O
A rare phosphate mineral with a characteristic blue-green color, forming radial aggregates of tiny crystals.
Properties
- Mohs hardness
- 5
- Color
- Blue; colorless
- Luster
- Vitreous
- Streak
- Weakly bluish
- Density
- 0
- Cleavage
- Parallel to (100)
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of burangaite are its blue-green color and typical occurrence in radial or spherical aggregates. The fibrous appearance of the clusters is also a good diagnostic indicator. ## Distinguishing from Similar Minerals Burangaite is sometimes confused with other secondary phosphates of similar color and habit, such as wavellite or turquoise. Wavellite forms very similar spherulitic aggregates but is usually lighter (greenish, yellowish, white) and has a lower hardness (3.5-4). Turquoise rarely forms radial aggregates with distinct crystals, more often occurring in cryptocrystalline and massive forms. ## Crystal Forms Crystals are tiny, acicular or bladed, elongated along one axis. They almost always occur in radial, stellate, or spherulitic aggregates, forming rosettes and spherical clusters on the surface of the host rock.
Geological environment
## Genesis Burangaite is a secondary phosphate mineral that forms in hydrothermal and weathering zones within complex granitic pegmatites rich in phosphates. It originates from the alteration of earlier phosphate minerals, such as beryllonite or apatite. ## Mineral Associations This mineral co-occurs with other phosphates, such as augelite, beryllonite, eosphorite, gatumbaite, lazulite, scorzalite, trolleite, as well as with quartz and microcline. ## Localities The most important and type locality is the Buranga pegmatite in the Gatumba District, Rwanda. It is also known from several other localities worldwide, including the Córrego Frio mine in Linópolis (Minas Gerais, Brazil) and the Cioclovina quarry in Romania.
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens by collectors are those with well-formed, spherical or radial aggregates of intense, blue-green color. Contrast with a light host rock (matrix) and the absence of damage to the delicate, acicular crystals are also important. The size of the aggregates is a key factor influencing value – specimens with rosettes exceeding one centimeter in diameter are rare and sought after. ## Popular Localities Undoubtedly, the most classic and valued specimens come from the type locality in Rwanda (Buranga pegmatite). Material from Brazil has also yielded good quality collector specimens.
Care and storage
## Cleaning Great caution is advised. It is safest to use compressed air to remove dust. If wet cleaning is necessary, use only distilled water and a very soft brush, then immediately and thoroughly dry the specimen. Ultrasonic cleaners should be avoided. ## What to Avoid Avoid contact with all chemicals, especially acids, which can damage the mineral. Burangaite is sensitive to high temperatures and prolonged exposure to strong light. It should not be soaked for extended periods. ## Storage Burangaite specimens, being fragile and often occurring on a delicate matrix, should be stored in separate, padded collector's boxes, protecting them from impacts and dust. They should be kept away from heat sources and direct sunlight.