Bobdownsite
Chemical formula: Ca<sub>9</sub>Mg(PO<sub>4</sub>)<sub>6</sub>(PO<sub>3</sub>F)
Bobdownsite is a rare phosphate mineral, distinguished by its complex chemical composition containing fluorine.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.13
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Trigonal
Diagnostic features
## Identification Identifying bobdownsite is extremely difficult without advanced research methods. Due to its occurrence as small, colorless grains, it is visually indistinguishable from many other minerals. Definitive identification requires chemical analysis (EDS/WDS) to confirm the presence of calcium, magnesium, phosphorus, and fluorine in appropriate proportions, and X-ray diffraction (XRD) methods to determine the crystal structure. ## Distinguishing from Similar Minerals Bobdownsite can be confused with other colorless phosphate minerals of the apatite group, such as fluorapatite or hydroxylapatite, as well as with quartz or calcite, with which it may co-occur. Differentiation relies on precise chemical analysis – the presence of magnesium and the specific phosphoro-fluoride group (PO₃F) is key. ## Crystal Forms This mineral forms exclusively anhedral, irregular grains. No well-formed crystals have been observed.
Geological environment
## Genesis Bobdownsite forms in complex phosphate pegmatites, which developed under low pressure and temperature conditions. It is a product of late-stage crystallization, likely resulting from metasomatism or hydrothermal processes affecting earlier phosphate minerals. ## Mineral Associations This mineral co-occurs with other phosphates, such as satterlyite, maricite, fluorapatite, wicksite, as well as with calcite and quartz. ## Localities The only confirmed locality for bobdownsite in the world is its type locality – the Big Fish River and Rapid Creek area in the Dawson mining district of Yukon, Canada. This is a classic locality for many rare phosphate minerals.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a bobdownsite specimen is determined not by the appearance of the mineral itself (which is inconspicuous), but by the richness of its associations and the confirmation of its presence through analysis. The most valuable samples are those where bobdownsite occurs alongside other rare phosphates from this locality. Identification by a reputable laboratory significantly increases the specimen's value. ## Popular Localities The only known and most prized specimens come from the Big Fish River / Rapid Creek area in the Canadian Yukon.
Care and storage
## Cleaning Due to the small size of the grains and their occurrence within other minerals, mechanical cleaning is usually neither possible nor necessary. For loose grains, compressed air can be used to remove dust. ## What to Avoid Avoid contact with strong acids, which can react with phosphates. Do not expose it to ultrasound or rapid temperature changes. ## Storage Specimens containing bobdownsite should be stored in stable conditions, in sealed boxes that protect against dust and mechanical damage. Direct exposure to sunlight should be avoided, although its sensitivity to UV radiation is not known.