Panasqueiraite
Chemical formula: CaMgPO<sub>4</sub>(OH)
Panasqueiraite is a rare mineral from the phosphate group, forming colorless to pinkish, bladed crystals, discovered in the famous Portuguese mines.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.21
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Panasqueiraite is identified by its characteristic habit – bladed, often fan-shaped crystals. Its color (colorless to pinkish), vitreous luster, and mineral associations are also helpful. However, definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other rare phosphates from Panasqueira, such as isoclasite or thadeuite, which form similar aggregates. "Eyeball" differentiation is practically impossible without knowing the exact finding location within the mine and comparing it with well-identified reference samples. It differs from them subtly in crystal habit and physical properties, which are, however, difficult to examine on microscopic specimens. ## Crystal Forms Crystals are monoclinic, with a bladed or tabular habit, elongated and flattened. They typically form radial, fan-shaped, or rosette-like clusters and aggregates. Single, well-formed crystals are rarely found.
Geological environment
## Genesis Panasqueiraite is a mineral of hydrothermal origin. It forms in the late stages of crystallization in alpine-type vein deposits, cutting through shales and greisens. It forms in rock cavities and fissures at relatively low temperatures. ## Mineral Associations This mineral co-occurs with many other phosphates and ore minerals. It is most commonly associated with apatite, fluorite, quartz, wolframite, chalcopyrite, arsenopyrite, thadeuite, isoclasite, and wolfeite. ## Localities The only confirmed and well-documented occurrence of panasqueiraite in the world is the Panasqueira mines (specifically the Barroca Grande Mine) in the Castelo Branco district, Portugal. This is its type locality and, so far, the only known one.
Rarity
Very rare
For collectors
## Quality Criteria The most prized panasqueiraite specimens are those with well-formed, fan-shaped aggregates of a distinct, pinkish color, contrasting with the matrix (most often quartz or schist). The size of the aggregates and the absence of mechanical damage significantly increase the specimen's value. Due to the microscopic nature of the crystals, specimens suitable for viewing without magnification are rare. ## Popular Localities The only source of collector's specimens is historical finds from the Panasqueira mines in Portugal. This mineral is not currently commercially mined, and specimens on the market come from old collections.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided, as they can damage brittle crystals. ## What to Avoid Contact with acids and other strong chemicals, which can react with phosphates, should be strictly avoided. The mineral is relatively stable, but prolonged exposure to moisture is not recommended. It should be protected from mechanical damage due to its brittleness and perfect cleavage. ## Storage Collector's specimens of panasqueiraite, often found on a delicate matrix, are best stored in sealed "membrane boxes" or in display cases away from dust and shocks. Due to the small size of the crystals, it is advisable to protect them from loss.