Mariakrite

Chemical formula: [Ca₄Al₂(OH)₁₂(H₂O)₄][Fe³⁺₂S²⁻₄]

Mariakryite is a newly discovered mineral from the hydrotalcite group, distinguished by a unique combination of iron, sulfur, calcium, and aluminum in its structure.

## Characteristics Mariakryite is a microscopic mineral, forming very small, platy crystals with a hexagonal outline. These crystals typically do not exceed 20 micrometers in size and often occur as aggregates or inclusions in calcite. Due to their size, visual features are difficult to observe without advanced equipment, such as a scanning electron microscope (SEM). When observed in this way, it appears as a dark, almost black mineral with a metallic luster. ## Physical properties Due to the microscopic size of the crystals, most physical properties, such as hardness, density, fracture, or cleavage, have not been determined. The luster is described as metallic, and the mineral is opaque. The streak is black. ## Colors and varieties The mineral is black. No varieties have been distinguished. ## History and name Mariakryite was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2023 (IMA2023-071). Its name honors Maria Krüger (born 1904, died 1999), a Polish writer and journalist. The discovery was made on archival material originating from the Hatrurim Formation in Israel. ## Uses Currently, mariakryite has no practical application and is solely an object of scientific and collecting interest for micromineral collectors.

Properties

Mohs hardness
3-3.5
Color
purple-brown
Luster
Metallic
Streak
Black
Density
2.005
Transparency
Opaque
Crystal system
Triclinic

Diagnostic features

## Identification Identification of mariakryite is possible only through advanced analytical methods, such as scanning electron microscopy (SEM) with EDS analysis or Raman spectroscopy. Under amateur conditions, identification is impossible. Characteristic features include microscopic, hexagonal, black lamellae occurring within calcite. ## Distinguishing from similar minerals Due to its unique chemical composition and occurrence, it is difficult to confuse it with other minerals after chemical analysis. Visually, without magnification, it is unrecognizable. ## Crystal forms Mariakryite forms very small, thin, platy crystals with a hexagonal habit, up to 20 μm in size and up to 2 μm thick. These crystals can occur individually or form small aggregates.

Geological environment

## Genesis Mariakryite forms under low-temperature alteration conditions within rocks of the Hatrurim Formation. It is a product of hydrothermal processes occurring in a calcium and sulfur-rich environment, with a low degree of oxidation. Its presence is associated with natural combustion and pyrometamorphism of sedimentary rocks. ## Mineral associations This mineral co-occurs primarily with calcite, in which it forms inclusions. It is also accompanied by other minerals from the Hatrurim Formation, such as larnite, brownmillerite, and ye'elimite. ## Localities The only confirmed locality of mariakryite in the world is its type locality - the Hatrurim Formation in the Negev Desert, Israel.

Rarity

Extremely rare

For collectors

## Quality criteria As a micromineral, the collector's value of a mariakryite specimen depends on the abundance of its occurrence and the possibility of identifying crystals on the rock matrix. The most desirable specimens are those on which numerous, well-formed (though still microscopic) crystals are visible, preferably analytically confirmed. Contrast with bright calcite enhances aesthetic appeal. ## Popular localities The only source of specimens is the Hatrurim Formation in Israel. Collector material is extremely rare and available almost exclusively through specialized channels.

Care and storage

## Cleaning Specimens of mariakryite, being microminerals, usually do not require cleaning. If cleaning is necessary, all mechanical methods should be avoided. Only careful use of compressed air to remove dust is permissible. ## What to avoid Avoid contact with chemicals, acids, and detergents. The mineral may be sensitive to changes in humidity and oxidation upon contact with air. It should not be heated or cleaned ultrasonically. ## Storage Specimens should be stored under stable conditions, in closed, airtight "micromount" boxes, to protect them from dust, mechanical damage, and humidity changes. Storage in a dry environment is crucial for maintaining the mineral's stability.

External references

Sources

Read more