Yushkinite
Chemical formula: (Mg,Al)(OH)<sub>2</sub>V<sup>3.6+</sup>S<sup>2-</sup><sub>2</sub>
Yushkinite is a very rare vanadium sulfide, characterized by a platy habit, metallic luster, and exceptional softness.
Properties
- Mohs hardness
- 1
- Luster
- Metallic
- Streak
- Red-brown
- Density
- 3.05
- Cleavage
- Perfect on {0001}
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Key diagnostic features of yushkinite include its platy or flaky habit, metallic luster, and characteristic brownish-red or purplish-pink color. The most important test is hardness – it is one of the softest minerals, scratchable with a fingernail. The flexible and sectile properties of its plates are also very characteristic. ## Distinguishing from Similar Minerals Yushkinite is sometimes confused with platy varieties of hematite (specularite), which is, however, much harder (5.5-6.5 on the Mohs scale) and has a red streak. Molybdenite has similar softness and habit, but its color is lead-gray, and it feels greasy to the touch. Native copper is malleable and has a different color and streak. ## Crystal Forms Yushkinite crystallizes in the trigonal system. It most often forms aggregates composed of thin, hexagonal plates, which can arrange into rosette-like forms. It is less commonly found as single, well-formed tabular crystals.
Geological environment
## Genesis Yushkinite is a hydrothermal mineral. It forms at low temperatures in calcite-quartz veins cutting through sedimentary rocks, such as clay shales and sandstones. ## Mineral Associations This mineral often occurs in association with other vein minerals. The most common associations include calcite, quartz, colorless and purple fluorite, as well as sulfides such as pyrite, sphalerite, and galena. ## Localities Yushkinite is an extremely rare mineral, known practically from only one locality in the world. This is its type locality – the Silova-Yakha River area on the Pai-Khoi Ridge, in the Nenets Autonomous Okrug, in the northern part of Russia. This is the only source for obtaining specimens of this mineral.
Rarity
Very rare
For collectors
## Quality Criteria The collector's value of yushkinite primarily depends on the abundance of the mineral on the specimen and the size and form of the aggregates. Specimens with distinct, large rosettes or dense clusters of plates with an intense, purplish-pink color are most highly prized. Aesthetic combination with other minerals, especially contrasting white calcite or purple fluorite, also enhances its attractiveness. ## Popular Localities The only place in the world from which collectible yushkinite specimens originate is its type locality on the Pai-Khoi Ridge in Russia. Specimens from this location set the standard for this mineral and are sought after by collectors of rare mineral species.
Care and storage
## Cleaning Yushkinite is extremely delicate and requires very careful handling. Cleaning should be kept to an absolute minimum. Only careful removal of dust with a soft brush or a stream of compressed air from a safe distance is permissible. Avoid any contact with water and other liquids. ## What to Avoid The mineral is extremely susceptible to mechanical damage due to its softness and perfect cleavage. Avoid contact with chemicals, acids, detergents, and water, which can damage its surface. Ultrasonic cleaners should not be used. It should also be protected from high temperatures. ## Storage Yushkinite specimens are best stored in sealed, padded "micromount" boxes to protect them from dust, physical damage, and humidity changes. When handling, use tweezers, grasping the specimen by the matrix rock, not directly by the delicate mineral plates.