Oyelite
Chemical formula: Ca<sub>5</sub>BSi<sub>4</sub>O<sub>13</sub>(OH)<sub>3</sub>·4H<sub>2</sub>O
Oyelite is a rare, hydrated calcium borosilicate, forming characteristic, silky white aggregates.
Properties
- Mohs hardness
- 5
- Luster
- Silky, Pearly
- Streak
- White
- Density
- 2.68
- Cleavage
- Perfect on {010}, good on {100}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification The most important diagnostic features of oyelite are its occurrence in the form of white, radially fibrous aggregates (spherulites) and its characteristic, silky luster. Hardness (5 on the Mohs scale) and the environment of occurrence (skarns) are also key indicators. ## Distinguishing from Similar Minerals Oyelite is sometimes confused with other white minerals with a fibrous habit, such as wollastonite, pectolite, or some zeolites (e.g., natrolite). It differs from wollastonite by its usually silkier luster and radial structure of aggregates. Pectolite forms similar aggregates but is harder. Final differentiation from visually similar minerals often requires advanced studies, e.g., chemical analysis to detect boron. ## Crystal Forms Oyelite crystallizes in the form of very fine, acicular or hair-like crystals, which almost always occur as radial, spherical or hemispherical aggregates. Single, well-formed crystals are extremely rare and appear as thin needles.
Geological environment
## Genesis Oyelite is a mineral of metamorphic origin. It forms in contact zones, within calc-silicate skarns, which develop at the interface of magmatic intrusions (e.g., granitoid) with carbonate rocks (limestones, marbles). ## Mineral Associations This mineral often co-occurs with other minerals typical of the skarn environment. Its most common associations include wollastonite, vesuvianite, diopside, grossular, calcite, and other calcium silicates and borosilicates. ## Localities The most important and classic oyelite localities are in Japan, in the Oye and Fuka mines in Okayama Prefecture. It is also known from the Bazhenovskoye deposit in the Urals, Russia, and the Crestmore quarry in California, USA. These are the few confirmed occurrences of this mineral worldwide.
Rarity
Very rare
For collectors
## Quality Criteria The most valued by collectors are specimens showing well-formed, spherical aggregates (spherulites) with a distinct, radial structure and intense, silky luster. The attractiveness of a specimen is enhanced by its size, color purity, and placement on a contrasting rock matrix, for example, accompanied by green vesuvianite or other colorful skarn minerals. ## Popular Localities The Japanese mines of Oye and Fuka are considered classic and provide the best quality material. Specimens from these localities are most sought after by collectors specializing in rare minerals or systematics.
Care and storage
## Cleaning Oyelite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, it can be rinsed in distilled water and then left to dry completely at room temperature. Ultrasonic cleaners should be avoided, as they can damage the delicate, fibrous aggregates. ## What to Avoid The mineral is sensitive to acids. As a hydrated mineral, it can undergo irreversible changes (dehydration) under high temperatures, so heating should be avoided. Brittle aggregates are susceptible to mechanical damage and chipping. ## Storage It is recommended to store specimens in closed boxes or display cases to protect them from dust and mechanical damage. Exposure to direct sunlight and sudden temperature changes should be avoided.