Ferriakasakaite-(La)
Chemical formula: CaLa³⁺Fe³⁺AlMn²⁺(Si₂O₇)(SiO₄)O(OH)
Ferriakasakaite-(La) is a very rare mineral from the epidote group, discovered in Japan, characterized by a complex chemical composition with lanthanum and iron.
Properties
- Mohs hardness
- 6.5
- Luster
- Vitreous
- Streak
- Light brown
- Density
- 4.16
- Cleavage
- Good on {001}
- Fracture
- Uneven
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of ferriakasakaite-(La) in field conditions or based on visual characteristics is impossible. This mineral requires advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) to determine its chemical composition, and X-ray diffraction (XRD) to confirm its crystal structure. Its brown color and occurrence in manganese skarns can be a preliminary indication. ## Distinguishing from similar minerals It can be confused with other brown minerals from the epidote group, such as allanite, epidote, or piemontite, as well as andradite. Differentiation is possible only through precise chemical analysis, which will reveal the unique combination of dominant lanthanum and trivalent iron. ## Crystal forms This mineral forms poorly developed, subhedral grains that combine into irregular aggregates. Well-formed, idiomorphic crystals have not been observed.
Geological environment
## Genesis Ferriakasakaite-(La) forms as a result of contact metamorphism processes. It occurs in skarns, which are rocks formed at the contact of a magmatic intrusion with carbonate-rich sedimentary rocks. It is found in zones rich in manganese and rare earth elements. ## Mineral associations This mineral is associated with minerals such as: bustamite, wollastonite, rhodochrosite, tephroite, aegirine, microcline, albite, andradite, and members of the epidote group. ## Localities The only confirmed locality (type locality) of ferriakasakaite-(La) in the world is the Fuka mine, located near Takahashi city, Okayama Prefecture, on Honshu Island, Japan.
Rarity
Extremely rare
For collectors
## Quality criteria As a "micromount" type mineral, whose identification is only possible in a laboratory, the main criterion for value is the confirmation of its identity by a reliable analytical laboratory. The attractiveness of a specimen is enhanced by the abundance of ferriakasakaite-(La) grains in the rock matrix and the presence of rare associated minerals. The size of the aggregates, although microscopic, is also important. ## Popular localities The only source of specimens is the Fuka mine in Japan. Material from this locality is highly valued by collectors specializing in rare minerals and minerals from specific type localities.
Care and storage
## Cleaning Due to its extreme rarity and occurrence as small grains intergrown with other minerals, mechanical cleaning of specimens is not recommended and should only be performed by specialists in laboratory conditions. The use of water or ultrasound may damage the delicate material. ## What to avoid Avoid contact with all chemicals, acids, and bases. Specimens should not be heated or subjected to sudden temperature changes. They should be protected from direct sunlight, which could potentially affect their structure. ## Storage Specimens containing ferriakasakaite-(La) should be stored under stable conditions, preferably in specialized, sealed "micromount" boxes, protecting them from dust, moisture, and mechanical damage. Storage in a dark and dry place is crucial for preserving the mineral's integrity.