Kalifersite
Chemical formula: K<sub>5</sub>Fe<sup>3+</sup><sub>7</sub>Si<sub>20</sub>O<sub>50</sub>(OH)<sub>6</sub>·12H<sub>2</sub>O
Kalifersite is a very rare, hydrated potassium and iron silicate, forming characteristic, platy aggregates with a brown color and pearly luster.
Description
## Characteristics Kalifersite is a complex, hydrated layered silicate (phyllosilicate) of potassium and iron. It forms very characteristic, flexible lamellae and platy aggregates, scaly or radial rosettes. Individual lamellae are extremely thin and resemble mica in appearance. Its color ranges from golden-brown to brown, often with a characteristic pearly luster on cleavage surfaces or silky in the case of fibrous aggregates. ## Physical Properties This mineral is very soft, with a Mohs hardness of approximately 2.5. It is light, with a density of 2.63 g/cm³. It possesses excellent, unidirectional cleavage, allowing for easy separation of thin, flexible lamellae. It is translucent, and on thin edges, it can be almost transparent. ## Colors and Varieties The dominant color of kalifersite is brown, often with a golden or reddish-brown hue. No color or commercial varieties have been distinguished. ## History and Name The mineral's name, approved by IMA in 2005, directly refers to its chemical composition: **Kali** (potassium, K), **fer** (iron, Latin *ferrum*), and **si** (silicon, Latin *silicium*). It was discovered on Mount Koashva within the ultra-alkaline Khibiny Massif on the Kola Peninsula in Russia. ## Applications Due to its extreme rarity, kalifersite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for advanced systematic and regional mineral collections.
Diagnostic features
## Identification Characteristic features of kalifersite include its golden-brown color, perfect mica-like cleavage, pearly luster, and occurrence in the form of platy or radial aggregates. A key diagnostic clue is its origin from alkaline pegmatites of the Khibiny Massif. ## Distinguishing from Similar Minerals Kalifersite can be confused with some micas (such as biotite or phlogopite) or other rare layered silicates. It differs from biotite by its lighter, often golden color and lower hardness. Precise identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Crystal Forms Kalifersite forms aggregates of thin, flexible lamellae, often arranged in radial rosettes, spherulites, or chaotic scaly clusters. It does not form well-developed, single crystals with visible faces.
Geological environment
## Genesis It is a hydrothermal mineral, crystallizing in the late stage of pegmatite evolution within ultra-alkaline (agpaitic) massifs. It forms in rock cavities and fissures. ## Mineral Associations Kalifersite coexists with other minerals typical of the Khibiny Massif pegmatites, such as aegirine, microcline, nepheline, lorenzenite, lamprophyllite, eudialyte, natrolite, and pectolite. ## Localities The only confirmed occurrences of kalifersite in the world are in Russia, on the Kola Peninsula. The type locality is Mount Koashva in the Khibiny Massif. This mineral is also found on the neighboring Mount Yukspor.
Rarity
Extremely rare
Collector aspects
## Quality Criteria As an extremely rare mineral, most often available as micro-mounts, its collectible value depends primarily on the richness of the aggregate and the aesthetics of the aggregates (e.g., well-formed rosettes). Specimens on matrix, accompanied by other rare minerals from this locality, are highly valued. The size of individual lamellae and the intensity of color also increase the attractiveness of the specimen. ## Popular Localities The only source of collectible specimens is the Khibiny Massif on the Kola Peninsula in Russia. Specimens from Mount Koashva and Mount Yukspor are the best known.
Care and storage
## Cleaning Kalifersite specimens should only be dry-cleaned, using a soft brush to remove dust. Due to the presence of water in its structure and its platy habit, contact with water, especially warm water, is absolutely inadvisable and can lead to the destruction of the specimen. ## What to Avoid Avoid contact with all chemicals, ultrasonic cleaners, and sudden temperature changes. The mineral is very soft and delicate, susceptible to mechanical damage (scratches, crushing of lamellae). It should not be exposed to direct sunlight. ## Storage It is recommended to store specimens in separate, padded membrane boxes or in micro-mount cases to protect the delicate lamellae from damage. It should be isolated from harder minerals.