Kutinaite
Chemical formula: Ag₆Cu₁₄As₇
Kutinaite is a very rare copper silver arsenide, forming small, metallic-lustered aggregates of a silvery-gray color.
Properties
- Mohs hardness
- 4.5
- Luster
- Metallic
- Density
- 8.38
- Transparency
- Opaque
- Crystal system
- Isometric
Diagnostic features
## Identification Identification of kutinaite is impossible without specialized equipment. Identification relies on chemical analysis (e.g., using an electron microprobe - EDS/WDS) to confirm the composition (presence of Ag, Cu, and As) and on metallographic studies under a reflected light microscope. Its silvery-gray color and high metallic luster are indications, but not uniquely identifying features. ## Distinguishing from Similar Minerals Kutinaite can be confused with many other arsenides and sulfarsenides of silver and copper, such as arsenic, domeykite, algodonite, or nováčekite, with which it often co-occurs. Differentiation is only possible based on precise chemical composition analysis and crystallographic data. ## Crystal Forms This mineral occurs exclusively as anhedral (irregular) grains and aggregates of microscopic size, usually not exceeding several hundred micrometers. It forms irregular veinlets and intergrowths in other minerals. It has not been observed in the form of well-developed crystals.
Geological environment
## Genesis Kutinaite is a hydrothermal mineral. It forms in ore veins, in zones enriched in arsenic, copper, and silver. Its crystallization occurs under low to medium temperature conditions. ## Mineral Associations This mineral co-occurs with other arsenides and ore minerals. In the type locality (Černý Důl), it was found in association with native arsenic, nováčekite, koutekite, domeykite, algodonite, chalcocite, bornite, native silver, and uraninite. ## Localities Kutinaite is an extremely rare mineral, known from only a few localities worldwide. The most important and type locality is the mine in Černý Důl in the Hradec Králové region of the Czech Republic. In addition, its occurrence has been confirmed in the Tsumeb mine in Namibia and in small quantities in other arsenide deposits.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a kutinaite specimen is determined not by the mineral itself (which is microscopic), but by the richness of the mineral association and the confirmation of its presence through analysis. The most valuable samples are those from the type locality (Černý Důl), containing rich aggregates of kutinaite visible under the microscope, along with other rare arsenides. The specimen must have analytical documentation confirming the mineral's identity. ## Popular Localities The only source of specimens of collector's significance is the historical type locality in Černý Důl in the Czech Republic. Specimens from this location are highly sought after by collectors specializing in rare minerals (so-called "systematists") and minerals from specific localities.
Care and storage
## Cleaning Due to its extreme rarity and microscopic grain size, kutinaite specimens are practically not subject to cleaning under amateur conditions. Any attempts at mechanical or chemical cleaning may irreversibly destroy the mineral or the surrounding rock matrix. Specimens should be treated solely as objects for microscopic observation. ## What to Avoid Avoid contact with any chemicals, acids, and bases. The mineral is sensitive to oxidation, so it should be protected from moisture and temperature changes. It should not be heated or exposed to ultrasound. ## Storage Kutinaite specimens should be stored under stable conditions, preferably in sealed containers (so-called micromount boxes), which protect against dust, moisture, and mechanical damage. Store away from heat sources and chemicals.