Kircherite
Chemical formula: (Na₅Ca₂K)(Si₆Al₆O₂₄)(S⁶⁺O₄)₂·0.33H₂O
Kircherite is a very rare mineral from the cancrinite group, distinguished by its intense blue color and occurrence as hexagonal crystals.
Properties
- Mohs hardness
- 5.5
- Color
- Colorless to light gray
- Luster
- Vitreous
- Streak
- White
- Density
- 2.42
- Cleavage
- {00.1}
- Fracture
- Irregular/Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Kircherite is primarily identified by its unique, intense blue color, hexagonal crystal habit, and specific occurrence environment. Vitreous luster and a light blue streak are also helpful diagnostic features. ## Distinguishing from Similar Minerals Kircherite can be confused with other blue minerals from the sodalite group, such as lazurite, haüyne, or nosean. Distinguishing it from these minerals often requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS/WDS), due to the similarity in color and habit. Lazurite usually occurs in calcitic marbles, often in association with pyrite, whereas kircherite is associated with volcanic rocks. ## Crystal Forms Kircherite crystallizes in the form of prismatic, hexagonal columns, often terminated by flat pinacoids. Crystals rarely occur individually; most often, they form radial or chaotic aggregates embedded in the rock.
Geological environment
## Genesis Kircherite is a mineral of volcanic origin. It forms in the late stages of crystallization within porous fragments (xenoliths) of silica-rich rocks that have been captured and altered by foid-bearing tephrites. It crystallizes in voids and fissures of these volcanic ejecta. ## Mineral Associations This mineral co-occurs with other rare minerals typical of this environment. It is most often accompanied by sanidine, leucite, diopside, andradite, as well as other minerals from the cancrinite-sodalite group, such as afghanite, liottite, and fantappièite. ## Localities The only confirmed and described locality of kircherite in the world (type locality) is the Valle Biachella quarry, located in the municipality of Sacrofano, near Rome, Italy. This is part of the Vulsini volcanic complex.
Rarity
Very rare
For collectors
## Quality Criteria The most highly prized kircherite specimens are those containing well-formed, sharply terminated crystals of intensely saturated blue color. Contrast with the light host rock (most often sanidinite) and the size and richness of crystal aggregates are also important. The presence of rare associated minerals can further increase the value of the specimen. ## Popular Localities The only source of kircherite specimens is its type locality: the Valle Biachella quarry in Italy. All specimens available on the collector's market come from this single location, which makes them exceptionally desirable.
Care and storage
## Cleaning Kircherite specimens, especially microminerals, should be cleaned with the utmost care. Compressed air is recommended to remove dust. If wet cleaning is necessary, use only distilled water and a very soft brush, avoiding strong rubbing. After cleaning, the specimen should be thoroughly dried. ## What to Avoid Contact with acids and other chemicals that can damage this complex aluminosilicate must be strictly avoided. The mineral is sensitive to sudden temperature changes. Prolonged exposure to strong sunlight is not advisable, although there is no conclusive evidence of fading. ## Storage Kircherite specimens, due to their small size and fragility, are best stored in specialized micromount boxes, which protect them from mechanical damage and dust. Avoid storage in humid environments.