Calcio-olivine
Chemical formula: Ca<sub>2</sub>SiO<sub>4</sub>
A rare calcium silicate from the olivine group, a polymorph of larnite, occurring mainly in metamorphic rocks and skarns.
Properties
- Mohs hardness
- 4.5
- Color
- Very light yellowish rose (caused by microinclusions of bernalite), colorless in thin sections
- Luster
- Vitreous
- Streak
- White
- Density
- 0
- Cleavage
- Good on {010}
- Fracture
- Conchoidal
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Identification of calcio-olivine in the field is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS), to distinguish it from other polymorphs of Ca₂SiO₄ (mainly larnite) and from other visually similar silicate minerals. ## Distinguishing from Similar Minerals Calcio-olivine is most often confused with larnite, with which it shares the same chemical formula. Differentiation is only possible based on crystal structure analysis. It can also be confused with other white or colorless skarn minerals, such as wollastonite, diopside, or grossular, from which it is distinguished by a set of physical (hardness, density) and chemical characteristics, verifiable only in a laboratory. ## Crystal Forms Calcio-olivine crystals are rare and usually poorly developed, with a tabular or platy habit. Most often, it occurs as grains or granular aggregates within the rock mass.
Geological environment
## Genesis Calcio-olivine is a high-temperature mineral, forming under conditions of contact metamorphism. It forms in skarns created at the contact of magmatic intrusions (e.g., gabbro) with limestones or dolomites. It is also found in some high-temperature volcanic rocks and in carbonate xenoliths within basaltic lavas. ## Mineral Associations This mineral often co-occurs with other calcium and magnesium silicates. Typical associated minerals include larnite, merwinite, spurrite, gehlenite, tilleyite, diopside, vesuvianite, and calcite. ## Localities Key confirmed localities for calcio-olivine include: - Scawt Hill in Northern Ireland and the Isle of Muck in Scotland (type locality). - The Lake Baikal region in Russia. - Riverside County in California, USA. - The Bellerberg volcanic complex in the Eifel Mountains, Germany. - Mount Somma in the Vesuvius complex, Italy.
Rarity
Very rare
For collectors
## Quality Criteria The collector appeal of calcio-olivine specimens is very specific and directed towards advanced collectors of rare minerals and those specializing in skarn minerals. Specimens with well-formed, even if small, crystals are most valued. A rich association with other rare minerals, such as larnite or spurrite, is also crucial. The clarity and transparency of crystals increase the value of a specimen, but due to its rarity, even granular aggregates in the matrix rock are sought after. ## Popular Localities The most classic and highly valued specimens by collectors come from historical localities in Scawt Hill (Northern Ireland) and from the Bellerberg volcanic complex (Germany), from which samples with well-studied mineral associations originate.
Care and storage
## Cleaning Calcio-olivine specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, compressed air can be used. Due to its potential reactivity, contact with water, and especially acids, should be avoided. ## What to Avoid Contact with acids (e.g., hydrochloric acid), which can quickly damage or destroy the mineral, must be absolutely avoided. It should also be protected from moisture, high temperatures, and sudden temperature changes. The mineral is brittle and sensitive to impact. ## Storage It is recommended to store specimens in dry conditions, preferably in closed, padded collector boxes or display cases, to protect them from dust, moisture, and mechanical damage. Exposure to direct sunlight should be avoided.