Chloro-potassic-ferro-edenite

Chemical formula: KCa<sub>2</sub>Fe<sup>2+</sup><sub>5</sub>(Si<sub>7</sub>Al)O<sub>22</sub>Cl<sub>2</sub>

An extremely rare mineral from the amphibole group, a potassium-chlorine variety of ferro-edenite, described from Algeria.

## Characteristics Chloro-potassic-ferro-edenite is a very rare mineral belonging to the amphibole group. It occurs as small, anhedral (irregularly formed) to subhedral (partially well-formed) grains, not exceeding 1 mm in size. It forms granular aggregates. It is black and opaque in mass, becoming translucent only in very thin fragments. It exhibits a vitreous luster. ## Physical Properties This mineral has a vitreous luster. It is opaque, and translucent in thin fragments. Its streak is light grayish-green. Due to its rarity and small crystal size, precise hardness and density values have not been determined. ## Colors and Varieties The only known color of this mineral is black. As a mineral defined by its unique chemical composition, it does not have any color varieties or commercial forms. ## History and Name The mineral's name directly refers to its chemical composition: "chloro" indicates the dominance of chlorine, "potassic" the presence of potassium, and "ferro" the dominance of iron. The name "edenite" refers to its belonging to the edenite series within amphiboles. It was officially recognized by the International Mineralogical Association (IMA) in 2015 (IMA2015-054). The type locality, meaning the first place of discovery, is the El-Aglab massif in Algeria. ## Applications Chloro-potassic-ferro-edenite has no industrial application. Its significance is purely scientific and collectible, as a unique member of the amphibole group.

Properties

Luster
Vitreous
Streak
Pale greyish green
Cleavage
Perfect on {110}
Fracture
Uneven
Transparency
Opaque, Translucent in thin fragments
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying this mineral is extremely difficult and practically impossible without advanced analytical techniques. Preliminary identification is based on its black color, vitreous luster, and occurrence in a specific geological environment (gabbro-norites). Certainty is only provided by chemical analysis (e.g., electron microprobe - EDS/WDS) confirming the presence of potassium, chlorine, and iron in appropriate proportions. ## Distinguishing from Similar Minerals Chloro-potassic-ferro-edenite is visually indistinguishable from many other black amphiboles, such as hornblende, arfvedsonite, ferro-edenite, or other rare species from this group. The differences lie in the chemical composition, which can only be examined under laboratory conditions. ## Crystal Forms This mineral forms irregularly or partially well-formed crystals up to 1 mm in size. It occurs as single grains or aggregates within the host rock.

Geological environment

## Genesis Chloro-potassic-ferro-edenite is an igneous mineral. It forms as a result of crystallization from magma within mafic intrusive rocks, specifically in gabbro-norites. ## Mineral Associations This mineral occurs in association with plagioclase, clinopyroxenes, and ilmenite. ## Localities The only confirmed locality of this mineral in the world is its type locality - the El-Aglab massif, Western Hoggar, Tamanrasset Province, Algeria.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, its collector's value depends on several factors. The most important is the richness of the specimen - the number of visible chloro-potassic-ferro-edenite grains on the rock matrix. Specimens where the mineral forms partially developed crystals (subhedral) and those showing clear associations with other minerals typical of the given locality are also valued. Precise documentation and confirmed identification are crucial. ## Popular Localities The only source of specimens is the type locality in the El-Aglab massif in Algeria. Material from this location is extremely difficult to obtain and is almost exclusively available through specialized channels.

Care and storage

## Cleaning Specimens of this mineral, usually in the form of micromounts, should be cleaned with the utmost care. For dust removal, it is best to use compressed air (in a can, from a safe distance) or a very soft brush. Avoid contact with water unless absolutely necessary. ## What to Avoid Ultrasonic cleaners and all chemical agents, acids, and detergents should be absolutely avoided. The mineral should be protected from sudden temperature changes and direct, prolonged exposure to sunlight. ## Storage The safest storage method is a specialized micromount box, which protects the small specimen from dust, moisture, and mechanical damage. A label with the name and location is a crucial element of a properly stored collection.

Sources

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