Slavíkite
Chemical formula: (H<sub>3</sub>O)<sup>1+</sup><sub>3</sub>Mg<sub>6</sub>Fe<sup>3+</sup><sub>15</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>21</sub>(OH)<sub>18</sub>·98H<sub>2</sub>O
Slavíkit is a very rare, hydrated magnesium and iron sulfate, forming characteristic yellow-green, hexagonal crystals and crusts.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous, Pearly
- Streak
- Light yellow
- Density
- 1.905
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Slavíkit can be identified by its characteristic yellow-green color, hexagonal outline of small, tabular crystals, and occurrence as crusts and efflorescences in the oxidation zones of sulfide deposits. A key diagnostic feature is its solubility in water. ## Distinguishing from Similar Minerals It can be confused with other secondary iron sulfates, such as jarosite or copiapite. It differs from jarosite by its lower hardness and hexagonal crystal form (jarosite is trigonal). It differs from copiapite by its crystal habit and often a lighter, more greenish hue. The water solubility test is helpful in distinguishing it from many similar minerals. ## Crystal Forms It forms thin, tabular crystals with a hexagonal outline. These crystals often group into rosette or radial aggregates. It also occurs as fine-grained, earthy, or powdery crusts and efflorescences.
Geological environment
## Genesis Slavíkit is a secondary mineral, formed by the weathering (oxidation) of sulfide iron deposits, especially pyrite and marcasite. It forms in a sulfate-rich environment, under low-temperature conditions, often as a product of mining activity (a mine mineral) on the walls of old workings and on mine dumps. ## Mineral Associations It most commonly co-occurs with minerals typical of sulfide deposit oxidation zones, such as gypsum, melanterite, halotrichite, epsomite, as well as with pyrite and marcasite themselves, from which it forms. ## Localities The most important and classic localities of slavíkit are in the Czech Republic, where it originates (Valachov near Skřiváň, Lom u Mostu). It is also known from several places in Germany (e.g., Thuringia), Hungary (near Recsk), and from a few localities in the USA (e.g., Iron County, Utah).
Rarity
Very rare
For collectors
## Quality Criteria The most valued by collectors are specimens with well-formed, sharp crystals with a hexagonal outline, forming attractive, rosette aggregates. An intense, vivid, yellow-green color and contrast with the rock matrix are important. Due to the rarity of the mineral, even rich crusts are sought after. ## Popular Localities Classic specimens, considered the best in the world, come from the Czech Republic, especially from the brown coal mines in the Most region (e.g., Lom u Mostu). They are the benchmark for this mineral and fetch the highest prices on the collector's market.
Care and storage
## Cleaning Slavíkit specimens are extremely sensitive to water, in which they readily dissolve. Wet cleaning is absolutely forbidden. Only very careful dust removal using a soft brush or a stream of compressed air from a distance is permissible. ## What to Avoid Avoid all contact with water, water vapor, and high humidity, which can lead to the dissolution and destruction of the mineral. It should also be protected from chemicals, high temperatures, and direct sunlight, which can cause fading and dehydration. ## Storage Slavíkit requires storage in conditions of controlled, low humidity. It is best kept in a sealed, airtight container (e.g., a "perky box") with a desiccant (silica gel). It should be displayed away from sources of heat and light.