Addibischoffite

Chemical formula: Ca₂Al₆Al₆O₂₀

Addibischoffite is an extremely rare oxide mineral, found exclusively as microscopic inclusions in diamonds.

## Characteristics Addibischoffite is a colorless, transparent mineral occurring as small, lath-shaped crystals, reaching up to 100 micrometers in length. Its uniqueness lies in the fact that it has only been identified as an inclusion within a natural diamond, making it one of the rarest minerals on Earth. Due to its microscopic size and unique occurrence environment, it does not form macroscopic specimens. ## Physical Properties This mineral is characterized by a relatively high hardness, estimated at 7.5 on the Mohs scale. It has a vitreous luster and is completely transparent. Its density, calculated based on its chemical composition and crystal structure, is approximately 3.33 g/cm³. ## Colors and Varieties Addibischoffite is colorless. No colored varieties have been observed to date. ## History and Name The mineral is named in honor of Prof. Addi Bischoff (born 1955), a German experimental petrologist from the University of Münster, for his contributions to meteorite research and high-pressure processes. The mineral was officially approved by the International Mineralogical Association (IMA) in 2017. The type material in which it was discovered comes from a diamond found in the Kankan region of Guinea. ## Applications Addibischoffite has no commercial or industrial applications. Its significance is purely scientific, providing valuable information about the conditions in the Earth's deep mantle where diamonds form.

Properties

Mohs hardness: 7.5
Luster: Vitreous
Streak: White
Density: 3.33
Cleavage: Perfect on {010}
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of addibischoffite is impossible without advanced analytical techniques. Due to its microscopic size and occurrence within diamond, recognition requires the use of methods such as Raman spectroscopy and chemical analysis using an electron microprobe (EMPA). Visual identification is excluded. ## Differentiation from Similar Minerals Addibischoffite may occur in association with other high-pressure minerals, such as coesite or kyanite. Distinguishing it from these and other mineral inclusions is only possible based on precise analysis of its chemical composition and characteristic Raman spectrum. ## Crystal Forms It forms elongated, lath-shaped crystals, which do not form larger aggregates or clusters.

Geological environment

## Genesis Addibischoffite crystallizes under extremely high pressure and temperature conditions, prevailing in the Earth's upper mantle at depths of hundreds of kilometers. It was trapped as an inclusion during diamond crystal growth and then brought to the Earth's surface by volcanic processes. ## Mineral Associations In its only known occurrence, addibischoffite coexists with other high-pressure minerals, such as coesite, kyanite, and grossular, which were also found as inclusions in the same diamond. ## Localities The only confirmed locality for addibischoffite in the world is its type locality – alluvial diamond deposits in the Kankan region of Guinea.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen in a collecting context is difficult to define, as the mineral is not available on the market. From a scientific perspective, any confirmed specimen is valuable. The size of the inclusion (up to 100 µm) and its quality (lack of fractures, good transparency) are important research parameters. ## Market Prices Addibischoffite is not traded on the collector's market. Specimens have purely scientific value and are held in research institutions. ## Popular Localities The only known locality is the Kankan region in Guinea. Material from this locality is not available to collectors.

Care and storage

## Cleaning Due to its occurrence exclusively as a microscopic inclusion in diamond, cleaning the mineral itself is neither possible nor necessary. Any maintenance activities pertain to the host diamond. ## What to Avoid The specimen is naturally protected by the surrounding diamond, which is the hardest known substance. However, extreme thermal shocks, which could theoretically damage the diamond or induce stress around the inclusion, should be avoided. ## Storage Storage concerns the diamond containing the addibischoffite inclusion. It should be stored in a safe place, similar to other valuable gemstones, preferably in a separate compartment or a padded box to prevent scratching other objects.

Sources

IMA Mineral List (CNMNC)