Pabstite
Chemical formula: BaSn<sup>4+</sup>Si<sub>3</sub>O<sub>9</sub>
Pabstite is a very rare barium and tin silicate, prized for its intense, blue-white fluorescence under ultraviolet light.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous
- Streak
- White
- Density
- 4.09
- Cleavage
- Poor on {1011}
- Fracture
- Conchoidal
- Transparency
- Transparent to Translucent
- Crystal system
- Hexagonal
Diagnostic features
## Identification The most important and unambiguous diagnostic feature of pabstite is its intense, chalky white or blue-white fluorescence under shortwave UV light. In daylight, it is inconspicuous and difficult to distinguish from other white minerals in the rock. It occurs in a specific geological environment, which also aids in identification. ## Distinguishing from Similar Minerals Within the host rock, pabstite can be confused with quartz, sanbornite, or other light silicates. However, the fluorescence test is conclusive. Co-occurring fresnoite also fluoresces, but yellow, which allows for easy differentiation under a UV lamp. ## Crystal Forms Pabstite most often forms anhedral (irregular) grains and aggregates embedded in the rock. Subhedral, partially developed, hexagonal crystals, usually not exceeding a few millimeters in size, are very rarely found.
Geological environment
## Genesis Pabstite is a mineral of metamorphic origin. It forms in contact zones, in complex skarns resulting from the metamorphism of barium- and silica-rich carbonate rocks (limestones), in the presence of tin mineralization. ## Mineral Associations This mineral occurs in association with other rare minerals such as sanbornite, fresnoite, walstromite, taramellite, as well as more common ones like quartz, diopside, and witherite. ## Localities The most important and classic pabstite localities are in California (USA), from where its holotype originates (Kalkar quarry in Santa Cruz County) and the best collector specimens (Rush Creek area in Fresno County). It is also reported from the Dara-i-Pioz complex in Tajikistan.
Rarity
Very rare
For collectors
## Quality Criteria The collector's value of pabstite specimens primarily depends on the intensity of its fluorescence and the richness of its occurrence in the matrix. The larger the rock surface that exhibits a strong, blue-white glow under UV light, the more valuable the specimen. An additional advantage, significantly increasing the value, is the presence of rare, partially developed crystals. ## Popular Localities Specimens from localities in Fresno County, California (USA), such as Esquire #7 and Esquire #8 Claims, are considered the best in the world. Most of the material available on the collector's market comes from there.
Care and storage
## Cleaning Pabstite specimens, usually as inclusions in rock, are best cleaned with a soft, dry brush to remove dust. If necessary, distilled water can be used. Due to its occurrence in a matrix, aggressive mechanical methods that could damage surrounding minerals should be avoided. ## What to Avoid Pabstite is a relatively stable silicate. However, contact with strong acids should be avoided. It is resistant to light and normal temperature changes, but extreme thermal shocks should be prevented. ## Storage Storage does not require special conditions. Specimens are best displayed in a dust-protected area. To fully appreciate its unique feature, it is worth equipping the display case with a shortwave UV light source.