Radtkeite
Chemical formula: Hg<sup>2+</sup><sub>3</sub>S<sup>2-</sup><sub>2</sub>ClI<sup>1-</sup>
Radtkeite is an extremely rare mercury mineral, a mercury iodide chloride sulfide, found in only one location in the world.
Properties
- Mohs hardness
- 2-3
- Luster
- Adamantine
- Streak
- Orange-red
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of radtkeite is possible almost exclusively under laboratory conditions using advanced techniques such as X-ray microanalysis (EDS/WDS) and X-ray diffraction (XRD). Field or collection identification is impossible. Characteristic features include its orange-red color, adamantine luster, and occurrence in association with other rare mercury minerals in a specific locality. ## Distinguishing from Similar Minerals It can be confused with other red or orange mercury minerals, such as cinnabar (HgS) or corderoite (Hg₃S₂Cl₂). However, cinnabar has a much more intense red color and higher density. Corderoite is visually very similar. Definitive differentiation requires chemical analysis to confirm the presence of iodine, which is a key component of radtkeite. ## Crystal Forms It forms very small, tabular or bladed crystals, which often combine into radial or rosette-like aggregates. Crystals rarely exceed 0.2 mm in length.
Geological environment
## Genesis Radtkeite is a hydrothermal mineral, formed at low temperatures. It crystallizes in vugs and fractures within highly brecciated and fractured silicified carbonate rock, which is a remnant of hot spring activity within a volcanic caldera. ## Mineral Associations It occurs in association with other rare mercury minerals, such as corderoite, perryite, kenhsuite, mcdermittite, eglestonite, kleinite, native mercury, as well as with cinnabar, opal, quartz, and calcite. ## Localities The only known occurrence of radtkeite in the world is its type locality – the McDermitt Mine (Cordero Mine) in Humboldt County, Nevada, USA.
Rarity
Extremely rare
For collectors
## Quality Criteria Due to its extreme rarity and microscopic size, any specimen containing visible, even under high magnification, radtkeite crystals is considered exceptional. Most highly valued are samples where well-formed, though still minute, crystal aggregates of intense orange-red color can be observed, contrasting with the rock matrix. Association with other rare mercury minerals is also important. ## Popular Localities The only source of radtkeite specimens is the McDermitt Mine in Nevada, USA. This mine is currently closed and reclaimed, making the acquisition of new material practically impossible. All available specimens come from old collections.
Care and storage
## Cleaning Due to its extreme rarity, small crystal size, and toxicity (mercury content), radtkeite specimens should not be cleaned by collectors. Any manipulation should be left to specialists under laboratory conditions. ## What to Avoid Absolutely avoid skin contact, inhalation of dust, and any attempts at chemical or mechanical cleaning. The mineral is sensitive to heat and strong light. As a mercury-containing mineral, it is highly toxic. ## Storage Specimens should be stored exclusively in sealed, clearly labeled containers (e.g., micromount type), away from light, heat sources, and moisture. They should be kept out of reach of children and pets, with a toxicity warning label.