Jasmundite
Chemical formula: Ca₁₁O₂(SiO₄)₄S²⁻
Jasmundite is a rare calcium silicate with sulfur, forming small, vitreous crystals of a characteristic greenish color.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.03
- Cleavage
- None
- Fracture
- Conchoidal,Sub-Conchoidal
- Transparency
- Transparent,Translucent,Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Amateur identification of jasmundite is practically impossible due to its small size and occurrence as inclusions. Recognition requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS/WDS). A preliminary indication may be its greenish color, vitreous luster, and co-occurrence with other minerals from the larnite-ellenbergerite group in a specific geological environment. ## Distinguishing from Similar Minerals Jasmundite can be confused with other fine-grained, green silicates found in similar parageneses, such as some minerals from the garnet or epidote group. Definitive differentiation is only possible based on chemical and crystallographic analysis. ## Crystal Forms Jasmundite crystals are very small, usually tabular or in the form of short, thick prisms. They often exhibit tetragonal dipyramid forms. They typically occur as single, isolated crystals or granular aggregates embedded in the host rock.
Geological environment
## Genesis Jasmundite is a metamorphic mineral. It forms under conditions of high temperature and low pressure, in contact zones where hot magma interacts with carbonate rocks (limestones, dolomites). It is a typical component of the sanidinite facies, developing in calcareous-silicate xenoliths within volcanic rocks. ## Mineral Associations This mineral often co-occurs with other rare high-temperature minerals such as larnite, mayenite, brownmillerite, spurrite, gehlenite, grossular, diopside, as well as calcite and apatite. ## Localities The most important and classic locality for jasmundite (type locality) is the Ettringer Feld in the Eifel volcanic region in Germany. It is found there in limestone xenoliths within leucite-tephrite lavas. Other confirmed localities include the Bellerberg volcano (also in Eifel), as well as some sites in Israel (Hatrurim Formation) and the Palestinian territories.
Rarity
Very rare
For collectors
## Quality Criteria The collecting appeal of jasmundite is primarily determined by the quality and size of its crystals, which is a rarity. Specimens with well-formed, sharp crystals of intense green color and good transparency are most highly valued. The contrast with the surrounding matrix and the presence of rare associated minerals are also important. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. ## Popular Localities By far the most valued and sought-after jasmundite specimens by collectors come from its type locality – Ettringer Feld in the Eifel volcanic complex in Germany. This is a classic locality for many rare contact minerals and provides the best-known specimens of this mineral.
Care and storage
## Cleaning Jasmundite specimens, due to their small size and fragility, should be cleaned with the utmost care. Compressed air is recommended for dust removal. If wet cleaning is necessary, use only distilled water and a very soft brush, avoiding strong friction. ## What to Avoid Avoid contact of the mineral with acids and other strong chemicals that may damage it. It should also not be subjected to ultrasonic or steam cleaning. Due to its moderate hardness, it must be protected from scratching by harder minerals. ## Storage The safest way to store jasmundite is to place it in a small, sealable "micromount" box, lined with soft material. This protects the specimen from mechanical damage, dust, and contact with other minerals in the collection.