Grahampearsonite
Chemical formula: Ca₂P₂O₇
Grahampearsonite is an extremely rare calcium pyrophosphate, discovered in Brazil, forming microscopic, colorless crystals with a tetragonal structure.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.107
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Identification of grahampearsonite is impossible without advanced analytical techniques, such as Raman spectroscopy and single-crystal X-ray diffraction (SCXRD). Visually, as microscopic, colorless, tabular crystals, it is indistinguishable from many other minerals included in diamond. ## Distinguishing from Similar Minerals As an inclusion in diamond, it can be confused with other colorless minerals, such as quartz, coesite, or other phosphates. Definitive differentiation requires analysis of chemical composition and crystal structure. ## Crystal Forms This mineral forms very small, thin, tabular crystals with tetragonal symmetry. These crystals occur as single, isolated lamellae on the surface of diamonds or as their inclusions.
Geological environment
## Genesis Grahampearsonite forms under ultra-high pressure conditions deep within the Earth's mantle. It has been identified as an inclusion in superdeep diamonds, indicating its crystallization at depths of hundreds of kilometers. Its presence is associated with metasomatic processes in the transition zone or lower mantle, where fluids rich in phosphorus and calcium interact with host rocks. ## Mineral Associations This mineral has been found in direct association with diamond. Other minerals typical of deep mantle environments, such as walstromite (CaSiO₃) and breyite (CaSiO₃ with a perovskite structure), have also been identified in its paragenesis. ## Localities The only confirmed occurrence (type locality) of grahampearsonite in the world is the Chapadão mine in the Juína region, Mato Grosso state, Brazil. This is a globally renowned locality for superdeep diamonds.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a specimen with grahampearsonite is inextricably linked to the quality of the diamond in or on which it occurs. The most valuable specimens are those where the microscopic grahampearsonite crystals are clearly visible, well-formed, and analytically confirmed. Scientific and collectible value here outweighs typical aesthetic criteria. ## Popular Localities The only source of specimens is the Juína region in Brazil. These specimens are highly sought after by specialized research institutions and a few advanced collectors of systematic minerals and diamond inclusions.
Care and storage
## Cleaning Due to the extremely small size of the crystals and their occurrence as inclusions or on the surface of other minerals (mainly diamonds), mechanical cleaning is neither recommended nor possible without specialized laboratory equipment. Specimens should be left in an untouched state. ## What to Avoid Avoid contact with any chemicals, acids, and bases. Do not expose specimens to ultrasound or rapid temperature changes. Protect them from any mechanical stress and scratching. ## Storage Specimens containing grahampearsonite, typically in the form of diamonds with inclusions, should be stored under stable conditions, in padded "perky boxes" to prevent mechanical damage. Protect them from dust and moisture.