Grguricite

Chemical formula: CaCr³⁺₂(CO₃)₂(OH)₄·4H₂O

Grguricite is a very rare, hydrated calcium chromium carbonate with a characteristic lilac color, forming microscopic, spherical aggregates.

## Characteristics Grguricite is a mineral from the dresserite group, chemically classified as a hydrated calcium chromium hydroxycarbonate. It occurs as microscopic, spherical aggregates (spherulites) with a radial internal structure, reaching sizes up to 0.2 mm. Due to the size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties Due to the microscopic nature of its occurrences, most physical properties, such as hardness, density, luster, or fracture, have not been precisely determined. The mineral is too small and delicate for standard tests. ## Colors and Varieties Grguricite is characterized by a uniform, lilac color. No color varieties or commercial forms are known. ## History and Name The mineral was described in 2021 by Igor V. Pekov and collaborators. Its name honors the Croatian mineralogist and geologist Stjepan Grgurić (born 1963) in recognition of his contributions to the study of chromium and platinum group element deposits. It was approved by the International Mineralogical Association (IMA) under number IMA2021-042. ## Uses Grguricite has no industrial applications. Its significance is purely scientific and collectible, as a unique and newly discovered mineral.

Properties

Crystal system
Triclinic

Diagnostic features

## Identification Amateur identification of grguricite is practically impossible. It requires advanced analytical methods, such as Raman spectroscopy or electron microprobe chemical analysis (EDS/WDS). A visual feature, observed under a microscope, is the characteristic lilac spherulites with a radial structure. ## Distinguishing from Similar Minerals Due to its unique chemical composition and color, it is unlikely to be confused with other minerals, especially after analysis. Visually, without magnification, it may resemble other secondary minerals forming coatings. ## Crystal Forms Grguricite forms exclusively spherical aggregates (spherulites) composed of microscopic, bladed or fibrous crystals arranged radially.

Geological environment

## Genesis Grguricite is a secondary mineral, formed in the oxidation zone (supergene zone) of hydrothermal deposits. In its type locality (Adeghoual, Morocco), it crystallizes in voids within dolomite, as a result of the weathering of primary chromium-bearing minerals. ## Mineral Associations At the type locality, it co-occurs with chromite, quartz, dolomite, barite, galena, sphalerite, chalcopyrite, goethite, malachite, cerussite, and hemimorphite. ## Localities The only confirmed occurrence of grguricite in the world is its type locality: Adeghoual, in the Mibladen area, Midelt Province, Morocco.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the quality of a specimen is primarily determined by the abundance and development of spherical aggregates on the rock matrix. Samples with numerous, well-separated spherulites of intense, lilac color, contrasting with the substrate, are most highly valued. The size of the aggregates, even if measured in tenths of a millimeter, also affects the value. ## Popular Localities The only source of specimens is the type locality in Morocco. Material from this location is extremely rare on the collector's market.

Care and storage

## Cleaning Grguricite specimens are extremely delicate and susceptible to mechanical damage. Cleaning is not recommended. Any attempts to remove dust should be limited to very careful use of a soft brush or a photographic air blower. ## What to Avoid Contact with water, chemicals (including acids and detergents), ultrasound, and sudden temperature changes should be absolutely avoided. The mineral is likely sensitive to dehydration. ## Storage Specimens should be stored under stable conditions, in closed "micromount" containers, protected from dust, moisture, and physical damage. They should not be exposed to direct sunlight.

External references

Sources

Read more