Dzharkenite
Chemical formula: Fe<sup>2+</sup>(Se<sub>2</sub>)<sup>2-</sup>
Dzharkenite is a rare iron selenide, forming microscopic, spherical aggregates with a metallic luster, related to the well-known pyrite.
Properties
- Mohs hardness
- 5
- Luster
- Metallic
- Streak
- Black
- Density
- 6.36
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Cubic
Diagnostic features
## Identification Identifying dzharkenite under amateur conditions is practically impossible. It requires specialized analytical equipment, such as a scanning electron microscope (SEM) with an EDS analyzer, to confirm its chemical composition (presence of only iron and selenium), and X-ray diffraction (XRD) to determine its crystal structure. A visual feature that might only suggest its presence are microscopic, metallic spherules on sedimentary rock. ## Distinguishing from Similar Minerals It can be confused with other microscopic minerals with a metallic luster, such as pyrite (FeS₂), marcasite (FeS₂), or other selenides. Pyrite rarely forms ideal spherules, more often cubes or framboids. Definitive differentiation is only possible through laboratory methods. ## Crystal Forms Dzharkenite forms characteristic, microscopic aggregates with a spherical or globular habit. These aggregates consist of radially arranged, fibrous or acicular crystals. Single, well-formed crystals with visible faces are extremely rare and observed only under high magnification.
Geological environment
## Genesis Dzharkenite is a mineral of sedimentary origin, forming under reducing conditions. It forms at low temperatures in organic-rich, carbonaceous clay and siltstone sediments. Its formation is associated with the activity of microorganisms that reduce selenates to selenides in the presence of iron. ## Mineral Associations At the type locality, dzharkenite co-occurs with calcite, ferroselite, mercury selenide (probably tiemannite), as well as amorphous carbonaceous matter and clay minerals. ## Localities Beyond the type locality in Kazakhstan (Sulucheq deposit), its occurrence has been confirmed in Niobrara Formation sediments in Wyoming (USA) and in Cretaceous sediments in Western Canada. All known occurrences are marine sediments rich in organic matter.
Rarity
Extremely rare
For collectors
## Quality Criteria As a micromount mineral, dzharkenite is valued primarily for the mere fact of its presence and confirmation on a specimen. The most highly rated samples are those where the spherical aggregates are numerous, well-isolated, undamaged, and contrast with the color of the matrix rock. The size of the aggregates, although always microscopic, is also important – larger spherules (close to 0.5 mm) are more desirable. ## Popular Localities The vast majority of specimens available on the collector's market come from the type locality in Kazakhstan. Specimens from North American localities are practically unavailable to private collectors and are mainly found in institutional collections.
Care and storage
## Cleaning Due to their microscopic size and rarity, dzharkenite specimens on matrix should generally not be cleaned mechanically or chemically. Any intervention may damage the delicate aggregates. If necessary, compressed air (from a safe distance) can be used to remove dust. ## What to Avoid Avoid contact with water, acids, cleaning agents, and ultrasound. The mineral is brittle, so it should be protected from impacts and vibrations. Prolonged exposure to humid air can lead to slow oxidation. ## Storage Micromount specimens should be stored in dedicated, sealed boxes (perky boxes) to protect them from dust, moisture, and mechanical damage. Storage under stable room conditions is fully sufficient.