Calciborite
Chemical formula: CaB<sub>2</sub>O<sub>4</sub>
Calcyborite is a rare borate mineral, forming colorless or white, acicular crystals with a silky luster, found in skarns.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous, Silky
- Streak
- White
- Density
- 2.89
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification The characteristic features of calcyborite are its forms of occurrence – most often as white, silky, fibrous or radial aggregates. Well-developed, prismatic crystals with a rhombic cross-section are also typical. Its genesis (occurrence in skarns) and co-occurrence with other borate minerals confirm its identification. ## Distinguishing from Similar Minerals Calcyborite can be confused with other white, fibrous minerals such as ulexite, colemanite, or some zeolites (e.g., natrolite). It differs from ulexite by the absence of the characteristic "television stone" effect. It differs from colemanite in crystal form and hardness. Unlike zeolites, calcyborite occurs in a specific skarn environment, not in gas vesicles in volcanic rocks. ## Crystal Forms Calcyborite crystals are prismatic, often elongated and acicular, with a rhombic cross-section. They usually form radial, stellate, or haphazardly tangled aggregates. Granular aggregates are less common.
Geological environment
## Genesis Calcyborite is a mineral of hydrothermal and metamorphic origin. It forms as a result of boron metasomatism in contact zones of magmatic intrusions with carbonate sedimentary rocks, such as limestones and dolomites. It forms within magnesian and calcic skarns. ## Mineral Associations This mineral often co-occurs with other borates, such as ludwigite, kotoite, szaibelyite (ascharite), sinhalite, as well as calcite, dolomite, magnetite, spinel, and minerals from the humite group. ## Localities The most important and classic localities for calcyborite are in Russia, in the boron deposits of Buryatia (Solongo deposit - type locality) and Siberia (Tayozhnoye). It also occurs in China (iron and boron ore mines in Liaoning), Japan (Fuka Mine, Okayama), North Korea (Hol Kol Mine), and the United States (New City Mine, California).
Rarity
Rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, transparent, prismatic crystals, especially if they are grouped into aesthetic, radial rosettes. Rich, pure white fibrous aggregates with a silky luster, contrasting with the dark matrix rock, are also attractive. Crystal size and lack of damage significantly increase the specimen's value. ## Popular Localities Specimens from Russian deposits (Solongo, Tayozhnoye) and from the Fuka Mine in Japan are considered classic and most desirable. Chinese localities have supplied many good quality specimens to the market in recent years, often in the form of radial aggregates on matrix.
Care and storage
## Cleaning Calcyborite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its brittleness and fibrous nature, ultrasonic cleaners and strong streams of water should be avoided. If water is necessary, it should be distilled water, and the specimen should be dried immediately and thoroughly. ## What to Avoid Avoid contact with acids, which can damage the mineral. Calcyborite is brittle, so it must be protected from impacts and falls. It should not be heated or exposed to sudden temperature changes. ## Storage Fibrous and acicular aggregates are very delicate, so it is best to store them in closed display boxes, lined with soft material, to protect them from dust and mechanical damage. Avoid storage in humid environments.