Radekškodaite-(La)

Chemical formula: (CaLa₅)(Al₄Fe₂+)[Si₂O₇][SiO₄]₅O(OH)₃

Radekškodaite-(La) is an extremely rare, black mineral of the allanite group, discovered in the Czech Republic and named after mineralogist Radek Škoda.

## Characteristics Radekškodaite-(La) is a very complex silicate from the epidote supergroup and allanite group. It was officially recognized as a new mineral species in 2021. It forms irregular, anhedral grains up to 1 cm in size, embedded in the host rock. It is characterized by a black color, vitreous to submetallic luster, and is opaque. Due to its recent discovery and extreme rarity, it is primarily an object of scientific research. ## Physical Properties This mineral is brittle, and its fracture is uneven. Its Mohs hardness has not yet been determined. The density calculated based on its chemical composition and unit cell parameters is 4.81 g/cm³. No cleavage has been observed. It has a grayish-black streak. ## Colors and Varieties The only known color of radekškodaite-(La) is black. No color varieties or commercial varieties have been distinguished. ## History and Name The mineral is named in honor of Dr. Radek Škoda (born 1978), a Czech mineralogist and geochemist from Masaryk University in Brno, in recognition of his contributions to the study of rare earth element minerals. It was discovered in a granitic pegmatite in Mirošov near Strážek in the Czech Republic, which is its only known locality (type locality). ## Uses Radekškodaite-(La) has no industrial applications. Its significance is purely scientific and collectible, especially for research institutions and collectors specializing in rare earth element minerals and specimens from type localities.

Properties

Luster: Vitreous to sub-metallic
Streak: Grayish-black
Density: 4.81
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying radekškodaite-(La) in the field or based on visual characteristics is practically impossible. Its key features include black color, vitreous to submetallic luster, lack of distinct crystal forms (occurrence as anhedral grains), and occurrence in granitic pegmatite. Definitive identification requires advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) to confirm its unique chemical composition with a dominance of lanthanum. ## Distinguishing from Similar Minerals This mineral can be easily confused with other black minerals found in pegmatites, such as schorl (black tourmaline), allanite-(Ce), ilmenite, or fergusonite. Distinguishing it from these minerals requires specialized laboratory equipment. Allanite-(Ce) has very similar properties but differs in the dominant rare earth element (cerium instead of lanthanum). ## Crystal Forms Radekškodaite-(La) does not form well-developed crystals. It occurs exclusively as anhedral (irregular) grains, which can reach up to 1 centimeter in size.

Geological environment

## Genesis Radekškodaite-(La) crystallizes in the late stages of granitic pegmatite evolution, in an environment enriched in rare earth elements (REE), aluminum, and iron. ## Mineral Associations This mineral is found in association with typical pegmatite rock minerals such as quartz, microcline, biotite, muscovite, and schorl. ## Localities The only confirmed occurrence of radekškodaite-(La) in the world is its type locality – a granitic pegmatite quarry near Mirošov, close to Strážek, in the Vysočina Region of the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare mineral, every analytically confirmed find is extremely valuable. The main criterion for value is the authenticity of the specimen itself. The size of the radekškodaite-(La) grain and the aesthetics of the host rock (matrix) are secondary factors. Specimens where the mineral is clearly visible and well-defined are most desirable for scientific and exhibition purposes. ## Popular Localities The mineral is known exclusively from one location in the world – its type locality in Mirošov, Czech Republic. There are no other localities from which collectible specimens originate.

Care and storage

## Cleaning Specimens of this mineral are extremely rare and usually occur as small grains within the rock. Cleaning, if absolutely necessary, should be limited to gently removing dust with a soft, dry brush. Avoid water and any chemical agents. ## What to Avoid As a brittle mineral, it is susceptible to mechanical damage, so impacts and drops should be avoided. It should not be subjected to ultrasound or rapid temperature changes. Due to its complex chemical composition, contact with acids and other aggressive chemicals should be avoided. ## Storage The safest way to store it is to place the specimen in a padded "micromount" box, which protects it from dust, light, and mechanical damage. A stable, dry environment and accurate labeling of the container are important due to the mineral's rarity and scientific value.

Sources

IMA Mineral List (CNMNC)