Shojiite
Chemical formula: Na(NaMg)Mg₅Si₈O₂₂(OH)₂
Shojiite is an extremely rare, colorless mineral from the amphibole group, discovered and known exclusively from a single locality in Japan.
Properties
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of shojiite is possible only through advanced laboratory methods, such as X-ray diffraction (XRD) and chemical analysis (e.g., electron microprobe). Under collecting or field conditions, identification is impossible. It occurs as colorless, fibrous crystals within the host rock. ## Differentiation from similar minerals Shojiite is visually indistinguishable from many other fibrous amphibole minerals, such as tremolite, actinolite, or other rare species. Differences can only be determined based on chemical composition and crystal structure analysis. ## Crystal forms It forms elongated, bladed, or fibrous crystals, which often arrange into felted or radial aggregates. Single, well-formed crystals are extremely rare and microscopic in size.
Geological environment
## Genesis Shojiite forms as a result of metamorphic processes. At its type locality, it was found in a rock that is a product of contact metamorphism, formed at the contact of ultramafic rocks (serpentinites) with a gabbro intrusion. It occurs in a sodium-rich reaction zone. ## Mineral associations Minerals co-occurring with shojiite at its discovery site include pargasite, clinochlore, titanite, zircon, apatite, and chromite. ## Localities The only confirmed and described occurrence of shojiite in the world is its type locality: Mamushinosawa stream, within Shibetsu city, Kamikawa subprefecture, Hokkaido island, Japan.
Rarity
Extremely rare
For collectors
## Quality criteria As a microscopic and extremely rare mineral, the only criterion of value for collectors is the confirmed presence of shojiite on a fragment of the host rock (matrix). Every specimen, regardless of "quality," is a valuable scientific and collecting acquisition. Specimens richer in fibers visible under the microscope will be more highly valued. ## Popular localities The only source of specimens is the type locality in Japan. The mineral is not available on the commercial market and is found mainly in the collections of scientific institutions and specialized micromount mineral collectors.
Care and storage
## Cleaning Due to its extreme delicacy and rarity, shojiite specimens should not be cleaned mechanically or chemically. Any attempts at cleaning may irreversibly destroy the mineral. They should be treated solely as microscopic objects. ## What to avoid Absolutely everything should be avoided: contact with water, chemicals, ultrasound, temperature changes, vibrations, and direct light. The mineral is extremely sensitive to all external factors. ## Storage Microscopic shojiite specimens should be stored exclusively in specialized, tightly sealed "micromount" boxes, under stable room conditions, away from sources of light, heat, and moisture. The safest place is a stable cabinet or drawer.