Clinoferroholmquistite

Chemical formula: &#₉₇₄₄;Li₂[Fe₂+₃Al₂]Si₈O₂₂(OH)₂

Clinoferroholmquistite is a very rare, dark green to black amphibole group mineral, occurring as acicular crystals.

## Characteristics Clinoferroholmquistite is a silicate group mineral, belonging to the lithium amphiboles. It forms elongated, prismatic, or acicular crystals, often aggregated into radial or tangled masses. Its color ranges from dark green, through blue-green, to almost black. It is an opaque mineral, only translucent on thin edges. ## Physical Properties This mineral is characterized by a hardness of 5-6 on the Mohs scale. It has a vitreous luster, which can be dull on fracture surfaces. Its density is approximately 3.12 g/cm³. It exhibits perfect cleavage in two directions, typical for amphiboles. ## Colors and Varieties Clinoferroholmquistite does not form color varieties or commercial forms. Its coloration is uniform and falls within the range of dark greens, with bluish or grayish-black hues. ## History and Name The mineral's name refers to its monoclinic (Greek: *klino*) symmetry, its iron content (Latin: *ferrum*), and its relation to the older mineral holmquistite. It was formally described as a new mineral species relatively recently, and its discovery is associated with studies of lithium pegmatites. ## Uses Due to its extreme rarity, clinoferroholmquistite has no industrial applications. It is solely an object of scientific interest and is valued by specialized collectors of rare minerals.

Properties

Mohs hardness: 5-6
Luster: Vitreous
Streak: Pale greenish gray
Density: 3.12
Cleavage: Perfect on {210}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying clinoferroholmquistite in the field is practically impossible without specialized equipment. In a collection, it can be preliminarily recognized by its dark green to black color, acicular crystal habit, and occurrence in lithium pegmatites. The characteristic angle between cleavage planes (approximately 124°), typical for amphiboles, is also distinctive. ## Distinguishing from Similar Minerals It can be confused with other dark amphiboles, such as hornblende, arfvedsonite, or riebeckite. It differs from hornblende by its often more acicular habit and specific environment of occurrence (lithium pegmatites). Distinguishing it from arfvedsonite and riebeckite, which also occur in similar parageneses, requires advanced chemical analyses (EDS/WDS) to confirm its composition with a dominance of iron and lithium. ## Crystal Forms Clinoferroholmquistite most often forms elongated, prismatic crystals with an acicular or fibrous habit. These crystals often occur as radial or chaotically tangled aggregates. Single, well-formed crystals are less common.

Geological environment

## Genesis It is an igneous mineral, crystallizing in the late stages from residual, lithium-, iron-, and volatile-rich melts within granitic lithium pegmatites. It forms under specific physicochemical conditions, which explains its rarity. ## Mineral Associations It most commonly co-occurs with minerals typical of lithium pegmatites, such as quartz, albite (especially the cleavelandite variety), microcline, spodumene, lepidolite, elbaite (lithium tourmaline), and amblygonite. ## Localities The most important and best-documented locality, from which the best specimens originate, is the Tanco pegmatite in Bernic Lake, Manitoba, Canada. This is the type locality for this mineral. It has also been reported in several other places worldwide, including Sweden and Italy, but specimens from these localities are much less known.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued specimens are those with well-formed, long needles, forming aesthetic, radial aggregates on a contrasting, light background (e.g., on white albite or quartz). The intensity of the color and the absence of damage to the delicate crystals are important. Large, rich clusters from the type locality (Tanco) command the highest prices. ## Popular Localities The only source of specimens of collector significance is the Tanco mine in Bernic Lake (Manitoba, Canada). Specimens from other localities are extremely rare and are primarily of scientific interest.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft brush to remove dust. For heavier dirt, compressed air can be used. The use of water is not recommended due to the possibility of damaging delicate aggregates. ## What to Avoid Avoid contact with all chemicals, including acids and bases. The mineral is brittle, so it should be protected from impacts, drops, and vibrations. It should not be heated or subjected to ultrasound. ## Storage It is recommended to store specimens in closed collector boxes, lined with soft material, to protect the acicular crystals from damage. Avoid areas with high humidity.

Sources

IMA Mineral List (CNMNC)