Bicchulite
Chemical formula: Ca<sub>2</sub>Al<sub>2</sub>SiO<sub>6</sub>(OH)<sub>2</sub>
Bicchulite is a rare mineral from the silicate group, forming small, white crystals with a regular structure, found in skarns.
Properties
- Mohs hardness
- 5.5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.74
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
Diagnostic features
## Identification Amateur identification of bicchulite is practically impossible due to the very small crystal size and its occurrence as fine-grained masses. It requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). Its occurrence in a specific geological environment (contact skarns) in association with other rare calcium-silicate minerals can be an indication. ## Distinguishing from Similar Minerals It can be confused with other white, fine-grained minerals from skarns, such as wollastonite, hydrogrossular, or other minerals from the sodalite group. Differentiation without specialized equipment is impossible. ## Crystal Forms It forms very small, poorly developed isometric crystals, most often in the form of rhombic dodecahedra. It usually occurs as massive aggregates, veins, or coatings composed of microscopic, rounded grains.
Geological environment
## Genesis Bicchulite is a low-temperature hydrothermal mineral, forming in zones of contact metamorphism. It forms in skarns created at the contact of carbonate rocks (limestones) with intrusions of igneous rocks, such as gabbro. It is a product of the alteration of pre-existing calcium-aluminum-silicate minerals, such as gehlenite, under conditions of elevated water activity. ## Mineral Associations It most often co-occurs with minerals such as: gehlenite, vesuvianite, wollastonite, afwillite, bultfonteinite, scawtite, and calcite. In the type locality (Fuka, Japan), it was found in association with gehlenite, spurrite, and vesuvianite. ## Localities The most important and confirmed occurrences of bicchulite worldwide are: - Japan - Fuka mine, Okayama Prefecture (type locality). - Northern Ireland - Carneal, County Antrim, and Scawt Hill, County Larne. - Israel - Hatrurim Formation in the Judean Desert. - Germany - Ettringer Bellerberg, Eifel. - Russia - in several localities in Siberia.
Rarity
Very rare
For collectors
## Quality Criteria The collector's appeal of bicchulite is determined mainly by its rarity and its connection to the type locality. Since the crystals are microscopic, specimens are not evaluated for aesthetics in the traditional sense. The most prized samples are those where bicchulite is well-identified and occurs in a rich association with other rare minerals from a known locality. Specimens with visible (even under high magnification) microcrystals are more desirable than massive aggregates. ## Popular Localities Specimens from the type locality in the Fuka mine in Japan are by far the most valued by collectors. Material from Northern Ireland (Carneal, Scawt Hill) also has historical and scientific significance.
Care and storage
## Cleaning Bicchulite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its brittleness and potential reactivity, washing in water, and especially the use of ultrasonics, should be avoided. ## What to Avoid Contact with acids, which can damage it, should be avoided. The mineral is sensitive to sudden temperature changes. It should be protected from impacts and scratches due to its moderate hardness and brittleness. ## Storage Collector's specimens of bicchulite, due to their small size and rarity, are best stored in enclosed "micromount" boxes, which protect them from dust, mechanical damage, and direct light.