Mukhinite
Chemical formula: Ca₂Al₂V³⁺(Si₂O₇)(SiO₄)O(OH)
Mukhinite is a rare, black mineral from the epidote group, being the vanadium analogue of clinozoisite, found in granular aggregates.
Properties
- Mohs hardness
- 8
- Color
- Black with a brownish tint
- Luster
- Vitreous
- Streak
- Pale brownish-gray
- Density
- 0
- Cleavage
- [001] perfect, [100] less so.
- Fracture
- Splintery
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of mukhinite include its black color, vitreous luster, and occurrence in fine-grained aggregates. Field identification is practically impossible without specialized equipment. Definitive identification requires advanced analytical methods, such as chemical analysis (EDS) to confirm the presence of vanadium, calcium, and aluminum, and X-ray diffraction (XRD). ## Distinction from Similar Minerals Mukhinite can be confused with other black, granular minerals, such as tourmaline (schorl), hornblende, or pyroxenes. Differentiation is based on hardness (higher than hornblende), lack of cleavage (tourmaline and hornblende exhibit it), and occurrence environment. Final distinction from other members of the epidote group, such as epidote or clinozoisite, is only possible through chemical analysis. ## Crystal Forms It most often forms irregular grains and massive, granular aggregates. Imperfectly formed, small prismatic crystals are rarely found.
Geological environment
## Genesis Mukhinite forms under conditions of contact metamorphism. It develops in skarns and rodingites, which formed at the contact of gabbroic intrusions with limestones. It is a product of metasomatism, a process of chemical alteration of rocks under the influence of hot, vanadium-rich solutions. ## Mineral Associations This mineral co-occurs with other minerals typical of vanadium skarns. It is most often associated with grossular (a vanadium-rich variety called goldmanite), diopside, titanite, ilmenite, apatite, roscoelite, and sulfides such as pyrite and chalcopyrite. ## Localities The most important and well-documented mukhinite localities worldwide include: - Russia: the type locality Tashelga in Gornaya Shoria, Siberia, and the Pereval vanadium ore deposit in the Eastern Sayan Mountains. - Japan: Mogurazawa mine in Gunma Prefecture on Honshu Island.
Rarity
Very rare
For collectors
## Quality Criteria For collectors, the most valuable specimens are those where mukhinite forms visible, well-formed, even if small, prismatic crystals. Rich granular aggregates, contrasting with a lighter matrix rock, e.g., with green grossular, are also highly prized. Analytically confirmed mineral identity is important. ## Popular Localities The most known and valued specimens come from the type locality in Russia (Tashelga) and from the Mogurazawa mine in Japan, from which samples with well-defined mineral associations originate.
Care and storage
## Cleaning It is recommended to clean mukhinite specimens only with a soft, dry brush to remove dust. The use of water, especially with detergents, is not advisable due to the lack of detailed data on its reactivity. ## What to Avoid Contact with chemicals, acids, and bases should be avoided. The mineral is brittle, so it must be protected from impacts and falls. There is no detailed information about its sensitivity to light or temperature, but it is generally recommended to avoid extreme conditions. ## Storage Mukhinite specimens are best stored in separate, padded display boxes to prevent scratching by harder minerals and mechanical damage. Due to the small size of the grains, it often occurs in matrix, which facilitates its display and storage.