Labuntsovite-Fe

Chemical formula: Na₄K₄Fe₂+₂Ti₄+₈(Si₄O₁₂)₄(O,OH)₈·₁₀-₁₂H₂O

Labuntsovite-Fe is a rare mineral from the silicate group, forming characteristic, prismatic crystals with a color ranging from orange-red to reddish-brown.

## Characteristics Labuntsovite-Fe is a complex silicate of titanium, sodium, potassium, and iron, belonging to the labuntsovite group. It forms well-developed, prismatic or acicular crystals, often gathered into radial or stellar aggregates. Specimens typically have an intense orange-red, reddish-brown, or yellowish-brown color. The crystals exhibit strong pleochroism, meaning a change in color depending on the viewing direction, from yellow to orange-red. ## Physical Properties This mineral is characterized by a hardness of 6 on the Mohs scale. It has a vitreous luster, and a greasy luster on fracture surfaces. It is a translucent mineral, rarely transparent. Its density ranges from 2.93-2.96 g/cm³. ## Colors and Varieties Labuntsovite-Fe occurs in shades from orange and reddish-orange to reddish-brown and yellowish-brown. No named color varieties or commercial varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition – it is an iron-rich (Latin: *ferrum*) member of the labuntsovite group. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 1998. Its discovery was made on material from the Khibiny Massif on the Kola Peninsula in Russia. ## Uses Labuntsovite-Fe has no industrial application. However, it is a valued and sought-after collector's stone due to its attractive crystals and rarity.

Properties

Mohs hardness: 6
Luster: Vitreous, Greasy
Streak: Pale orange
Density: 2.93-2.96
Cleavage: Good on {100}
Fracture: Uneven
Transparency: Translucent to transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Labuntsovite-Fe can be identified by its characteristic crystal habit – prismatic or acicular, often forming radial aggregates. Key features also include an intense orange-red to reddish-brown color, vitreous luster, and occurrence in a specific geological environment (alkaline massifs). ## Distinguishing from Similar Minerals It can be confused with other minerals from the labuntsovite group, such as labuntsovite-Mn. Differentiation requires advanced chemical analysis (EDS/WDS) to determine the dominant element (in this case, iron). It is distinguished from eudialyte by a different crystal habit (eudialyte forms tabular crystals in the trigonal system) and usually a different color. ## Crystal Forms Crystals are typically elongated, prismatic, with a cross-section close to square. They often occur as radial or stellar aggregates, as well as single, overgrown crystals in rock fissures.

Geological environment

## Genesis Labuntsovite-Fe is a mineral of hydrothermal origin. It forms in the late stages of crystallization in pegmatites and hydrothermal veins cutting nepheline syenites and other alkaline rocks. It crystallizes in voids and fissures within these rocks. ## Mineral Associations This mineral co-occurs with other rare minerals typical of alkaline massifs. It is most often associated with natrolite, analcime, aegirine, microcline, lorenzenite, eudialyte, and other minerals from the labuntsovite group. ## Localities The most important and well-known localities for labuntsovite-Fe worldwide are in Russia, on the Kola Peninsula, in the alkaline massifs of Khibiny (Oleniy Ruchey mine, Koashva mountain) and Lovozero (Karnasurt mountain, Kedykvyrapakh mountain). These are the places from which the best collector's specimens originate.

Rarity

Rare

For collectors

## Quality Criteria The most highly valued labuntsovite-Fe specimens are those with sharp, well-terminated, and undamaged crystals of intense orange-red color. Radial aggregates ("sunbursts") on a light rock matrix that contrasts with the crystal color are particularly sought after. The size of the crystals and the aesthetic appeal of the entire specimen's composition are also important. ## Popular Localities By far the most prized specimens come from the Khibiny and Lovozero massifs on the Kola Peninsula in Russia. Specimens from these localities, especially from the Oleniy Ruchey mine and Koashva mountain, are considered the global standard for this mineral.

Care and storage

## Cleaning Labuntsovite-Fe specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. After wet cleaning, the specimen should be thoroughly dried. ## What to Avoid Avoid contact with acids and other aggressive chemicals that can damage the crystal surface. The mineral is relatively hard but brittle, so it should be protected from impacts and falls. It is not sensitive to sunlight. ## Storage Collector's specimens of labuntsovite-Fe, especially those with well-formed, delicate crystals, are best stored in separate, padded boxes or display cases to prevent mechanical damage and abrasion.

Sources

IMA Mineral List (CNMNC)