Letovicite
Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>3</sub>H(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>
Letovicite is a rare, water-soluble ammonium sulfate, forming colorless or white efflorescences and small crystals, most often as a result of coal dump fires.
Properties
- Mohs hardness
- 1
- Luster
- Vitreous to Pearly
- Streak
- White
- Density
- 1.78
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification The key diagnostic feature of letovicite is its water solubility. Even a small drop causes its destruction. Other important features include extreme softness (Mohs hardness 1), very low density, and occurrence in a specific environment – on burning coal dumps or as a product of volcanic exhalations. It reacts with sodium hydroxide solution, releasing ammonia with a characteristic odor. ## Distinguishing from similar minerals Letovicite can be confused with other white, secondary sulfates, such as mascagnite ((NH₄)₂SO₄) or tschermigite ((NH₄)Al(SO₄)₂·12H₂O). Distinguishing them often requires advanced research methods, such as chemical or X-ray analysis. It differs from gypsum by its much lower hardness and complete water solubility. ## Crystal forms Letovicite crystallizes in the triclinic system. It forms small, tabular or bladed crystals, often grouped into rosette-like or radial aggregates. Most often, however, it is found in the form of fine-grained, loose or compact efflorescences and crusts.
Geological environment
## Genesis Letovicite is a secondary mineral with a specific genesis. It is mainly formed as a result of fires on coal dumps and storage sites. It forms at temperatures from 50 to 150°C in the process of reaction of volatile ammonia (formed from the decomposition of organic matter in coal) with sulfur oxides (originating from the oxidation of pyrite and other sulfides). The second environment of its occurrence is volcanic exhalations (fumaroles), where it crystallizes from hot gases rich in sulfur and ammonia compounds. ## Mineral associations This mineral often co-occurs with other ammonium sulfates, such as mascagnite, boussingaultite, and tschermigite. In the environment of burning dumps, it is also accompanied by native sulfur, sal ammoniac (ammonium chloride), and realgar. ## Localities The most important letovicite localities in the world are associated with mining activities. Besides the type locality in Letovice in the Czech Republic, it is known from burning dumps near Pécs in Hungary, in Kladno (Czech Republic), and in several places in Pennsylvania (USA). Occurrences associated with volcanism have been reported, among others, on the La Fossa volcano on Vulcano island in Italy.
Rarity
Rare
For collectors
## Quality criteria The collector's value of letovicite primarily stems from its rarity. The most prized specimens are those with well-formed, even small crystals, forming visible aggregates. Due to the mineral's fragility and instability, undamaged, well-preserved specimens from classic, confirmed localities (such as Letovice or Pécs) are the most sought after. The presence of associated minerals, such as native sulfur or other rare sulfates, also enhances the specimen's attractiveness. ## Popular localities The most classic and desired by collectors are specimens from the type locality in Letovice, Czech Republic, and from the coal mine near the city of Pécs, Hungary, where relatively large crystalline aggregates were found.
Care and storage
## Cleaning Letovicite is water-soluble, so **it must not be cleaned wet**. Any contact with water, even in the form of vapor, can damage or completely destroy the specimen. Only very careful dust removal with a soft, dry brush or a stream of compressed air from a distance is permissible. ## What to avoid Above all, water and moisture should be avoided. The mineral is hygroscopic, meaning it absorbs moisture from the air, which leads to its dissolution. It should be protected from all chemicals, acids, and detergents. It is very soft and brittle, so it is susceptible to mechanical damage. ## Storage Letovicite specimens require special storage conditions. They should be kept in tightly sealed, dry containers (e.g., "perky box" type). It is advisable to place a moisture-absorbing agent (e.g., silica gel) in the container. They should be stored at a stable temperature, away from direct sunlight and heat sources.