Iangreyite
Chemical formula: Ca₂Al₇(PO₄)₂(PO₃OH)₂(OH,F)₁₅·8H₂O
Iangreyite is an extremely rare, hydrated calcium aluminum phosphate, forming tiny, hexagonal crystals of white or colorless hue.
Properties
- Mohs hardness
- 3
- Color
- Colourless, white, cream, yellowish, light pink
- Luster
- Vitreous
- Streak
- White
- Density
- 2.46
- Cleavage
- On {001}
- Fracture
- Irregular/Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of iangreyite is impossible without advanced analytical techniques. Identification requires chemical analysis (EDS) and X-ray structural analysis (XRD) to confirm its unique composition and crystal structure. Visually, at the occurrence site, it can be suspected based on the presence of tiny, white, rosetted aggregates in association with other rare phosphates. ## Distinguishing from similar minerals It can be confused with other white or colorless secondary phosphate minerals, such as wardite, crandallite, or wavellite, which can form similar spherulitic aggregates. Differentiation is only possible through laboratory analysis. ## Crystal forms Iangreyite forms thin, tabular crystals with a hexagonal outline. These crystals almost always occur as radial, rosetted, or spherulitic (spherical) aggregates.
Geological environment
## Genesis Iangreyite is a secondary phosphate mineral. It forms in the oxidation zones of phosphate deposits, as a result of hydrothermal solutions interacting with aluminum-rich rocks. In the type locality (Silver Coin mine), it formed in voids in quartz. ## Mineral associations This mineral co-occurs with other, often rare, phosphate minerals. At the Silver Coin mine in Nevada, it was found in association with crandallite, opal, quartz, strengite, and wardite. At Tom's mine in South Australia, it occurs with wavellite, crandallite, and cacoxenite. ## Localities Iangreyite has been confirmed in only two locations worldwide, making it an extremely rare mineral. These are: - Silver Coin Mine, Valmy, Humboldt County, Nevada, USA (type locality). - Tom's Phosphate Mine, Kapunda, South Australia, Australia.
Rarity
Extremely rare
For collectors
## Quality criteria The quality of an iangreyite specimen primarily depends on the richness and aesthetics of its microscopic crystal aggregates. Most prized are specimens showing well-formed, isolated rosettes or dense coverings of spherulites on a contrasting matrix (e.g., dark quartz). The size of the aggregates, though always microscopic, is also important – larger rosettes are more desirable. Purity (lack of damage to delicate crystals) is crucial. ## Popular localities Both known localities provide collectible specimens, with material from the Silver Coin mine in Nevada being the type material and historically the first. Specimens from both locations are equally highly valued by collectors specializing in "micromount" minerals.
Care and storage
## Cleaning Iangreyite specimens are extremely delicate and brittle. Any mechanical cleaning, including the use of brushes or compressed air, should be avoided as it could damage the microscopic crystals. If cleaning is absolutely necessary, the specimen can be carefully immersed in distilled water and then left to air dry completely at room temperature. ## What to avoid Contact with acids and other chemicals should be strictly avoided. The mineral is very soft (Mohs hardness 1), so it is susceptible to scratching even by the gentlest tools. It should be protected from high temperatures, which can cause the loss of water from its structure and destruction of the crystals. ## Storage Iangreyite specimens should be stored exclusively in stable, sealed "micromount" containers to protect them from dust, mechanical damage, and sudden changes in humidity. They should not be exposed to direct sunlight.