Clino-ferro-suenoite

Chemical formula: &#₉₇₄₄;Mn₂+₂Fe₂+₅(Si₈O₂₂)(OH)₂

Silicate from the amphibole group, characterized by its dark color and occurrence in metamorphic rocks rich in iron and manganese.

## Characteristics Clino-ferro-suenoite is a mineral from the silicate class, belonging to the amphibole supergroup. It is a complex silicate of magnesium, iron, and manganese. It forms prismatic, acicular, or fibrous crystals, which often occur in radial, tangled aggregates or as massive forms. Its color is typically dark green, greenish-black to black. It is characterized by a vitreous luster on crystal surfaces and cleavage planes. ## Physical Properties The mineral's hardness on the Mohs scale is 5.5 to 6, placing it on par with many other amphiboles. It is relatively dense, with a specific gravity ranging from 3.3 to 3.5 g/cm³. It exhibits excellent prismatic cleavage in two directions, typical for amphiboles, intersecting at angles of approximately 56° and 124°. It is a brittle mineral, and its fracture is uneven, often splintery in the case of fibrous aggregates. It is translucent in thin fragments to completely opaque in thicker masses. ## Colors and Varieties This mineral does not show much color variability, remaining in the range from dark green to black. No colored or commercial varieties are known. ## History and Name Clino-ferro-suenoite was formally described and recognized as a new mineral species in 2003 by Mariko Nagashima and Minoru Tamada. Its name is tripartite: the "clino" component refers to its monoclinic crystallographic system, "ferro" indicates the dominance of iron (Latin: ferrum) at specific positions in the crystal structure, and "suenoite" is the root name of the series, derived from the Suwa mine in Japan, which is the type locality. ## Applications Clino-ferro-suenoite has no industrial applications. Its significance is purely scientific and collectible, as a rare member of the complex amphibole group.

Properties

Mohs hardness: 5.5-6
Luster: Vitreous
Streak: Pale grey-green
Density: 3.3-3.5
Cleavage: Perfect on {110}
Fracture: Uneven to splintery
Transparency: Translucent to opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Helpful identification features include: dark green to black color, vitreous luster, prismatic or fibrous habit, and excellent amphibole cleavage. A key clue is the occurrence environment – metamorphic rocks rich in manganese and iron. ## Distinguishing from Similar Minerals Macroscopic distinction of clino-ferro-suenoite from other dark amphiboles, such as grunerite, ferro-actinolite, or some hornblendes, is practically impossible without advanced studies. Grunerite is its analog without dominant manganese. Definitive identification requires chemical analysis (e.g., EDS) or X-ray diffraction (XRD) studies. ## Crystal Forms It most often forms elongated prismatic, acicular, or fibrous crystals. These often occur as radial or tangled aggregates. Well-formed, isolated crystals are rare.

Geological environment

## Genesis It is a metamorphic mineral, forming under conditions of regional or contact metamorphism. It typically forms in rocks rich in iron and manganese, such as metamorphosed banded iron formations (BIF) and manganese skarns. ## Mineral Associations It often co-occurs with other minerals characteristic of manganese-rich environments, such as spessartine (garnet), rhodonite, pyroxmangite, dannemorite, quartz, and other amphiboles. ## Localities The most important occurrences of this mineral include its type locality – the Suwa mine in Iwate Prefecture, Japan. It is also known from some metamorphic regions in Sweden (e.g., the Harstigen mine in Värmland) and from the famous Broken Hill deposit in New South Wales, Australia.

Rarity

Rare

For collectors

## Quality Criteria For collectors, specimens with well-formed, sharp crystals with a distinct luster are most valuable. Since such forms are rare, rich radial or fibrous aggregates are also prized. The attractiveness of a specimen is enhanced by a contrasting rock matrix or association with other minerals, e.g., pink rhodonite or red spessartine. ## Popular Localities Specimens from the type locality in Japan have historical value. Those from the Broken Hill deposit in Australia are considered among the best in terms of crystallization quality.

Care and storage

## Cleaning Clino-ferro-suenoite specimens are best cleaned dry with a soft brush. For heavier soiling, distilled water can be used. Ultrasonic cleaners should be avoided, as vibrations can cause cracking along cleavage planes. ## What to Avoid The mineral is sensitive to strong acids. It should be protected from scratching by harder minerals, such as quartz (hardness 7). It is stable under normal temperature conditions and is not sensitive to light. ## Storage Store in separate, padded boxes or display cases to prevent abrasions and scratches. Due to its visual similarity to many other dark amphiboles, it is crucial to keep the label with the specimen's name and locality.

Sources

IMA Mineral List (CNMNC)