Ferrovalleriite
Chemical formula: 2(Fe,Cu)S·1.53[(Fe²⁺,Al,Mg)(OH)₂]
Ferrovalleriite is a very rare, soft iron and copper sulfide with a characteristic dark brown color and metallic luster.
Properties
- Mohs hardness
- 1
- Luster
- Metallic
- Streak
- Black
- Density
- 3.72
- Cleavage
- parallel to {001}
- Fracture
- Step-Like
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Ferrovalleriite can be identified by its characteristic dark brown color, metallic luster, very low hardness (1 on the Mohs scale), and black streak. Its occurrence in the form of fine, scaly aggregates is also a diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with other minerals from the valleriite group, from which it requires advanced chemical analyses (EDS/WDS) to distinguish. It differs from graphite by its brown hue and higher density. It is distinguished from pyrrhotite by its significantly lower hardness and lack of magnetic properties. ## Crystal Forms It typically forms microscopic, hexagonal plates and scales. It occurs as dense, felted or earthy aggregates, and also as inclusions in other minerals, mainly sulfides.
Geological environment
## Genesis Ferrovalleriite is a hydrothermal mineral. It forms as a result of the alteration of earlier copper and iron sulfides in magmatic deposits. It is a product of relatively low-temperature hydrothermal processes that occur after the crystallization of major ore minerals. ## Mineral Associations It most commonly co-occurs with other copper and iron sulfides. In its type locality, it has been found alongside chalcopyrite, talnakhite, mooihoekite, pentlandite, as well as magnetite and serpentine group minerals. ## Localities The most important and best-documented occurrence of ferrovalleriite is its type locality – the Oktyabrsky Mine in the Norilsk region on the Taimyr Peninsula, Russia. This is the only known place in the world where it occurs in quantities allowing its identification and collection of microscopic specimens.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a ferrovalleriite specimen is determined by the richness of its occurrence on the rock matrix and the possibility of identification under magnification. The most valued samples are those where the mineral forms visible, dense aggregates with a distinct brown coloration and metallic luster, contrasting with the surrounding minerals. Due to its microscopic nature, the purity and form of individual crystals are not key criteria. ## Popular Localities The only source of collector specimens is its discovery locality – the Oktyabrsky Mine in Russia. Specimens from this locality are extremely difficult to acquire and appear on the market very rarely.
Care and storage
## Cleaning Ferrovalleriite specimens are extremely delicate and soft. Any mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water or other liquids is not recommended. ## What to Avoid Contact with water, chemicals, acids, and detergents must be strictly avoided. The mineral is very soft, so it should be protected from scratches, impacts, and abrasion. It should not be heated or exposed to ultrasound. ## Storage Specimens should be stored in stable conditions, in a closed, padded collector's box, to protect them from mechanical damage, dust, and moisture. It is best to store it separately to prevent it from being scratched by harder minerals.