Lobanovite

Chemical formula: K<sub>2</sub>Na(Fe<sup>2+</sup><sub>4</sub>Mg<sub>2</sub>Na)Ti<sup>4+</sup><sub>2</sub>(Si<sub>4</sub>O<sub>12</sub>)<sub>2</sub>O<sub>2</sub>(OH)<sub>4</sub>

Lobanovite is a rare, dark green to black mineral from the astrophyllite group, forming tabular crystals and radial aggregates.

## Characteristics Lobanovite is a complex potassium, sodium, iron, magnesium, and titanium silicate, belonging to the astrophyllite group. It occurs as tabular, lath-like crystals, which often form radial or stellate aggregates. Its color is typically dark green, brownish-green to almost black. The mineral is opaque and exhibits a characteristic luster. ## Physical Properties Lobanovite has a hardness of approximately 3 on the Mohs scale. Its crystals are brittle. It exhibits perfect cleavage in one direction, which is visible on crystal surfaces. The luster is vitreous to metallic. ## Colors and Varieties This mineral has no distinct color varieties or commercial forms. Its coloration is quite consistent, ranging from dark green, through brown, to black. ## History and Name Lobanovite was named in honor of Konstantin Vladimirovich Lobanov (born 1930), a Russian geologist from the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry of the Russian Academy of Sciences in Moscow. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2018 (IMA2018-054). Its discovery is relatively recent. ## Uses Due to its rarity and small crystal sizes, lobanovite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists.

Properties

Mohs hardness
3
Luster
Vitreous to submetallic
Streak
Greenish brown
Density
3.35
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent to opaque in thin fragments, Opaque
Crystal system
Triclinic

Diagnostic features

## Identification Characteristic features of lobanovite include its dark green to black color, tabular crystal habit, and tendency to form radial aggregates. Perfect cleavage in one direction and vitreous-metallic luster are also important indicators. ## Distinguishing from Similar Minerals Lobanovite is very similar to other minerals from the astrophyllite group, especially astrophyllite itself. Distinguishing it requires advanced analytical methods, such as chemical analysis (EDS/WDS) or X-ray diffraction (XRD), as the differences lie in the proportions of key elements (magnesium, iron, sodium). ## Crystal Forms It forms flattened, tabular, or lath-like crystals, often grouped into fan-shaped, radial, or stellate aggregates. Crystals rarely occur as single, well-formed individuals.

Geological environment

## Genesis Lobanovite is a mineral of magmatic origin. It forms in the late stages of crystallization in alkaline or peralkaline magmatic intrusions, such as nepheline syenites and associated pegmatites. ## Mineral Associations It most commonly co-occurs with minerals typical of alkaline environments, such as microcline, nepheline, aegirine, eudialyte, lamprophyllite, and other minerals from the astrophyllite group. ## Localities The type and so far main locality, from which the best-studied specimens originate, is the Khibiny Massif on the Kola Peninsula in Russia. This is a classic locality for many rare alkaline minerals.

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp crystals forming aesthetic, radial or stellate aggregates are most valued by collectors. Contrast with a light matrix rock (e.g., white nepheline or microcline) significantly enhances the specimen's attractiveness. The size of the aggregates and the intensity of the luster are also important. ## Popular Localities The only significant source of collectible lobanovite specimens is the Khibiny Massif on the Kola Peninsula in Russia.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its perfect cleavage, avoid washing under running water and using ultrasonic cleaners. If liquid is necessary, a brief immersion in distilled water and immediate drying is recommended. ## What to Avoid Avoid contact with acids and other chemicals. The mineral is brittle, so it must be protected from impacts and falls. Do not subject it to sudden temperature changes. ## Storage Lobanovite specimens are best stored in individual, padded display boxes to protect them from mechanical damage and scratching by other minerals. Avoid exposure to humid environments.

Sources

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