Rasmussenite

Chemical formula: Ca(C<sub>2</sub>H<sub>3</sub>O<sub>3</sub>)<sup>1-</sup><sub>2</sub>·3H<sub>2</sub>O

Rasmussenite is an extremely rare, organic mineral, a hydrated calcium pyruvate, found in lake sediments.

## Characteristics Rasmussenite is an organic mineral with a unique chemical composition. It forms very small, colorless, lath-like crystals, usually not exceeding 0.3 mm in length. It is observed as individual crystals dispersed in sediments. ## Physical Properties Rasmussenite crystals exhibit a vitreous luster. They are transparent and colorless. Due to its small size and rarity, many of its physical properties, such as hardness or density, have not been precisely determined. ## History and Name The mineral was named after Kaare Lund Rasmussen (born 1958), a Danish astrophysicist and archaeometrist, who first synthesized this compound in the laboratory. It was approved by the IMA in 2013. ## Applications Due to its extreme rarity and microscopic size, rasmussenite has no practical applications and is solely an object of scientific interest and for specialized collectors of organic minerals.

Properties

Luster
Vitreous
Streak
White
Cleavage
Perfect on {100}
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of rasmussenite is impossible without advanced analytical methods, such as X-ray diffraction (XRD) or spectroscopy. Visually, at the occurrence site, only tiny, colorless crystals in the sediment can be observed. ## Distinguishing from similar minerals It can be confused with other colorless, fine-grained secondary minerals found in sediments, such as gypsum. Certain differentiation requires specialized laboratory equipment. ## Crystal forms Rasmussenite forms elongated, lath-like or acicular crystals.

Geological environment

## Genesis Rasmussenite is a biogenic mineral, forming under anaerobic conditions in lake bottom sediments. Its formation is associated with the decomposition processes of organic matter. ## Mineral associations It co-occurs with calcite, pyrite, and other organic minerals, such as julienite and calclacite, within laminated lake sediments (gyttja). ## Localities The only known occurrence (type locality) is Bølling Sø lake in central Jutland, Denmark.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of a rasmussenite specimen depends solely on the presence of identifiable, even microscopic, crystals within the original sedimentary matrix. Every analytically confirmed specimen is extremely valuable scientifically. ## Popular localities The only source of specimens is the type locality in Denmark, making them virtually unavailable on the collector's market.

Care and storage

## Cleaning Due to extreme delicacy and water solubility, rasmussenite specimens should not be wet cleaned. The safest method is to remove dust with a soft brush or a photographic air blower. ## What to avoid Contact with water, acids, bases, and other chemicals that can immediately dissolve or damage the crystals must be strictly avoided. The mineral is sensitive to changes in temperature and humidity. ## Storage Specimens should be stored under stable conditions, in a sealed, dry container (e.g., a "perky box"), away from direct sunlight and heat sources. It is best to store it in the original sedimentary material in which it was found.

Sources

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