Clinotobermorite
Chemical formula: Ca<sub>5</sub>Si<sub>6</sub>O<sub>17</sub>·5H<sub>2</sub>O
A rare calcium silicate of the tobermorite group, forming microscopic, colorless or white crystals and fibrous aggregates.
Properties
- Mohs hardness
- 4.5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.49-2.52
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identifying clinotobermorite is extremely difficult without advanced research methods, such as X-ray diffraction (XRD) or spectroscopy. In collections, it is primarily recognized based on its label and confirmed locality. Visually, it is characterized by white, fibrous, or radial aggregates in a specific geological environment. ## Distinguishing from Similar Minerals It can be confused with other minerals from the tobermorite group (tobermorite, tobermorite-11Å), as well as with other white, fibrous silicates such as okenite, pectolite, or wollastonite. Definitive differentiation is almost exclusively possible through laboratory analysis. ## Crystal Forms It forms elongated, bladed, or acicular crystals up to several tens of micrometers long. These crystals combine into radial, spherulitic, or fibrous aggregates, and also form thin coatings and veins.
Geological environment
## Genesis Clinotobermorite is a low-temperature hydrothermal mineral. It forms in altered calcium-rich rocks, such as skarns, marbles, or metamorphosed manganese deposits. It can also crystallize in voids and fissures in volcanic rocks. ## Mineral Associations It most often co-occurs with other calcium silicates and hydrothermal minerals. In its type locality (Wessels Mine), it was found in association with calcite, hematite, ettringite, brucite, and hydroxylellestadite. ## Localities The most important and best-documented occurrence of clinotobermorite is its type locality – the Wessels Mine in Hotazel, in the Kalahari Manganese Field in the Republic of South Africa. It is also known from several other locations worldwide, including Fuka in Japan and the Omsukchan region in Russia.
Rarity
Very rare
For collectors
## Quality Criteria The quality of clinotobermorite specimens is primarily assessed based on the richness and aesthetics of the aggregates. Specimens with well-formed, spherical or radial clusters, contrasting with the color of the host rock, are most valued. Association with other rare minerals is also important. Due to the microscopic size of the crystals, their individual form is not a key criterion. ## Popular Localities By far the most known and valued specimens come from the Wessels and N'Chwaning mines in the Kalahari region of South Africa. Material from these localities is considered reference for this species.
Care and storage
## Cleaning Clinotobermorite specimens are very delicate and brittle. Cleaning should be limited to an absolute minimum. If necessary, a very soft brush can be used to remove loose dust. Avoid water and any chemicals. ## What to Avoid Absolutely avoid contact with water, acids, and other chemicals that can damage or dissolve the mineral. Aggregates are sensitive to shock and ultrasound. It should not be heated, as it can easily lose water from its crystal lattice, leading to its destruction. ## Storage Specimens should be stored in stable conditions, in sealed containers or display cases, to protect them from dust, moisture, and mechanical damage. Due to its brittleness, it should not be in direct contact with other minerals.