Fizélyite
Chemical formula: Ag<sup>1+</sup><sub>5</sub>Pb<sup>2+</sup><sub>14</sub>Sb<sup>3+</sup><sub>21</sub>S<sup>2-</sup><sub>48</sub>
Fizélyite is a rare lead-silver sulfosalt, forming acicular or prismatic crystals with a metallic luster.
Properties
- Mohs hardness
- 2.5
- Luster
- Metallic
- Streak
- Black
- Density
- 5.5-5.6
- Cleavage
- Good on {100}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of fizélyite include its metallic luster, lead-gray color, black streak, and crystal habit – elongated, acicular, or prismatic, often with longitudinal striations. Its high density is also a helpful indicator. It occurs in a specific environment – in hydrothermal veins with other sulfosalts. ## Distinguishing from Similar Minerals Macroscopic distinction of fizélyite from other similar sulfosalts (e.g., andorite, jamesonite, zinkenite) is extremely difficult and often impossible without advanced research, such as chemical analysis (EDS) or X-ray diffraction (XRD). Initially, it was even considered a variety of andorite. Key for identification is the analysis of mineral association and a thorough examination of crystal morphology. ## Crystal Forms Crystals are monoclinic, with a prismatic or acicular habit. They are strongly elongated and striated parallel to the crystallographic c-axis. Most often, they form radial, fan-shaped, or chaotically entangled aggregates embedded in the host rock.
Geological environment
## Genesis Fizélyite is a mineral of hydrothermal origin. It forms in the final stages of crystallization in ore veins forming at low and medium temperatures. ## Mineral Associations It most commonly co-occurs with other sulfosalts, such as andorite, semseyite, freieslebenite, pyrargyrite, and miargyrite. It is also accompanied by quartz, calcite, dolomite, pyrite, and sphalerite. ## Localities The most important and classic locality for this mineral is the Herja mine in Chiuzbaia (Romania). Significant specimens also come from the Bulldog Mountain mine in Creede, Colorado (USA). It has also been reported in Příbram (Czech Republic), in some areas of Bolivia (Potosí department), and in Japan (Chichibu mine, Saitama prefecture).
Rarity
Very rare
For collectors
## Quality Criteria For collectors, specimens with well-formed, sharp, and undamaged crystals are most desirable. Rich aggregates of acicular or prismatic crystals are highly valued, especially those embedded in a contrasting matrix, such as white quartz or calcite. The size of the crystals and the aesthetics of the entire specimen significantly influence its value. ## Popular Localities The most prized specimens by collectors come from the type locality – the Herja mine in Romania, which has provided the best-known crystals of this mineral. Attractive, though usually smaller, specimens have also been found in Creede, Colorado.
Care and storage
## Cleaning Fizélyite specimens should be cleaned very carefully, preferably dry, using a soft brush to remove dust. Contact with water should be kept to a minimum; if necessary, use distilled water and immediately dry the specimen thoroughly. Ultrasonic cleaners should not be used. ## What to Avoid The mineral is soft and susceptible to scratching. Avoid contact with harder minerals. As a sulfosalt, it is sensitive to chemicals, including acids and strong detergents. Prolonged exposure to moisture can lead to oxidation and tarnishing of the surface. ## Storage It is recommended to store specimens in a dry place, preferably in closed boxes or display cases, to protect them from dust, moisture, and mechanical damage. Avoid sudden temperature changes.