Lisetite

Chemical formula: Na₂CaAl₄(SiO₄)₄

Lisetite is a very rare, colorless tectosilicate of sodium, calcium, and aluminum, occurring as microscopic inclusions in eclogite rocks.

## Characteristics Lisetite is a mineral from the tectosilicate group, chemically classified as a sodium, calcium, and aluminum silicate. It forms microscopic, colorless grains or flakes, which typically occur as inclusions in other minerals, such as omphacite. Due to its size, visual characteristics are difficult to observe without specialized equipment, such as a polarizing microscope. It is transparent and has a vitreous luster. ## Physical Properties Due to its extreme rarity and microscopic nature of occurrence, many physical properties of lisetite, such as hardness, density, cleavage, or fracture, have not yet been precisely measured. The mineral is transparent and characterized by a vitreous luster. ## Colors and Varieties Lisetite is colorless. No colored or commercial varieties are distinguished. ## History and Name The mineral's name comes from its type locality – the Liset eclogite occurrence in the municipality of Selje, Norway, where it was discovered. It was described in 1986 by Smith and Cheeney. The International Mineralogical Association (IMA) approved it as a new mineral in the same year. ## Uses Lisetite has no industrial or commercial applications. Its significance is purely scientific and collectible, as a unique component of high-pressure metamorphic rocks.

Properties

Luster
Vitreous
Density
0
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of lisetite is impossible without advanced analytical techniques. This requires analysis of thin rock sections under a polarizing microscope and the use of methods such as X-ray microanalysis (EDS/WDS) or electron backscatter diffraction (EBSD) to confirm its chemical composition and crystal structure. In collecting practice, identification relies on trust in the label and the supplier's reputation. ## Distinguishing from Similar Minerals Under the microscope, lisetite can be confused with other colorless rock-forming minerals, such as quartz, plagioclase, or cordierite. Differentiation requires specialized analytical studies, as its optical properties may be similar to other silicates. ## Crystal Forms Lisetite forms very small, tabular or platy crystals, often with irregular outlines. It usually occurs as individual grains dispersed in the host rock, mainly in omphacite.

Geological environment

## Genesis Lisetite is a metamorphic mineral, formed under conditions of very high pressure and relatively high temperature, typical of the eclogite facies. It forms as a result of reactions occurring in aluminum-rich crustal rocks that have undergone subduction to significant depths. ## Mineral Associations This mineral co-occurs with other high-pressure minerals. In its type locality, it was found in association with omphacite (in which it forms inclusions), garnet (pyrope-almandine), kyanite, coesite, rutile, talc, dolomite, jadeite, and potassium feldspars. ## Localities The only confirmed and described occurrence of lisetite in the world is its type locality: the Liset eclogite lens, near Selje, on the Stad peninsula in the Vestland region of Norway.

Rarity

Extremely rare

For collectors

## Quality Criteria Since lisetite is a microscopic mineral, its collectible value is not assessed based on typical criteria such as color, size, or clarity of a single crystal. The most valuable are rock fragments (eclogite) from the type locality, where the presence of lisetite has been analytically confirmed. The value of a specimen is therefore closely linked to its origin and scientific documentation. ## Popular Localities The only source of specimens is the type locality in Liset, Norway. Material from this location is extremely difficult to obtain and appears on the collector's market sporadically, mainly circulating among specialized collectors and scientific institutions.

Care and storage

## Cleaning Specimens containing lisetite (usually rock fragments) can be cleaned with a soft brush and distilled water to remove dust and loose contaminants. Aggressive mechanical methods that could damage the host rock should be avoided. ## What to Avoid Contact with strong acids and bases, which could react with co-occurring minerals, should be avoided. There is no detailed data on sensitivity to light or temperature, but standard caution and avoidance of extreme conditions are recommended. ## Storage Specimens containing lisetite are best stored in stable conditions, in closed boxes or display cases, to protect them from dust and mechanical damage. It is important to include a label with the precise locality, as its scientific and collectible value is closely tied to it.

External references

Sources

Read more