Katerinopoulosite

Chemical formula: (N₃-H₄)₂Zn₂+(S₆+O₄)₂·₆H₂O

Katerinopoulosite is a rare, water-soluble hydrated zinc ammonium sulfate, forming colorless efflorescences in old mines.

## Characteristics Katerinopoulosite is the natural analogue of the synthetic compound known as zinc ammonium sulfate hexahydrate and belongs to the Tutton's salt group. It occurs as small, often imperfectly formed crystals, as well as fine-grained efflorescences and crusts. It is a colorless to white mineral with a vitreous luster. Due to its water solubility, it is unstable in humid environments. ## Physical Properties This mineral is characterized by low hardness, approximately 2-2.5 on the Mohs scale, and a low density of about 1.93 g/cm³. It is transparent to translucent. Its most characteristic physical property is its complete solubility in water, which is crucial for its storage and care. ## Colors and Varieties Katerinopoulosite is a colorless or white mineral. No colored varieties or trade names are distinguished for it. ## History and Name The mineral is named in honor of Athanasios Katerinopoulos (born 1951), a professor of mineralogy and petrology at the University of Athens, in recognition of his contributions to mineralogical research in the Lavrion area of Greece. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2016. The type locality is the Kamariza mines in Lavrion. ## Uses Katerinopoulosite has no industrial applications. Its significance is purely scientific and collectible, being of interest mainly to specialists in rare secondary minerals and systematists.

Properties

Mohs hardness: 2-2.5
Luster: Vitreous
Streak: White
Density: 1.93
Cleavage: Perfect on {010}
Fracture: Conchoidal
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying katerinopoulosite under amateur conditions is very difficult. Key clues include its occurrence environment (efflorescences in old mine workings), co-occurrence with other secondary sulfates, and white color. The most important diagnostic feature is its complete solubility in water. However, definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from Similar Minerals Katerinopoulosite can be easily confused with many other white, secondary sulfates that form efflorescences, such as bianchite, epsomite, goslarite, or other Tutton's salts. Goslarite (ZnSO₄·7H₂O) is chemically similar but does not contain ammonium ions. Visual distinction from these minerals is practically impossible without specialized chemical analyses. ## Crystal Forms It crystallizes in the monoclinic system, forming short, prismatic crystals. However, it is most often found as very fine crystals forming loose or compacted efflorescences and crusts on rocks in dry parts of mines.

Geological environment

## Genesis It is a secondary mineral of post-mining genesis. It forms in dry, sheltered parts of old mine workings as a result of the reaction of acidic, sulfate-rich waters (formed from the oxidation of sulfide ores, mainly sphalerite) with solutions containing ammonia. The source of ammonia is most often decomposing organic matter, such as bat guano. ## Mineral Associations Katerinopoulosite co-occurs with other rare, secondary zinc and magnesium sulfates that form under similar conditions. Its typical associated minerals include bianchite, gunningite, epsomite, goslarite, and gypsum. ## Localities The most important and typical occurrence of this mineral is the historical mines in the Lavrion (Laurion) region of Attica, Greece, particularly the Kamariza mine. It is a mineral with a very limited range of occurrence, and specimens come almost exclusively from this single locality.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, katerinopoulosite is primarily valued by specialized collectors of rare and systematic minerals. Specimens with well-formed, sharp, and transparent crystals are most highly rated, even if their size is submillimeter. Documentation confirming the mineral's identity and an aesthetic association with other rare species on the same sample are also important. ## Popular Localities The only source of collectible katerinopoulosite specimens is its type locality - the mines in the Lavrion region of Greece. Specimens from this location are the standard for this mineral.

Care and storage

## Cleaning The mineral is completely soluble in water, so under no circumstances should it be wet cleaned. Any contact with water or alcohol will cause its destruction. Cleaning is generally not recommended. If necessary, dust can be very carefully removed with a soft, dry brush or a gentle stream of compressed air from a distance. ## What to Avoid Contact with water, water vapor, and high humidity must be strictly avoided, as these can cause the mineral to deliquesce. It should also be protected from high temperatures, which can lead to its dehydration and decomposition. Exposure to direct sunlight is not recommended. ## Storage Katerinopoulosite specimens must be stored in dry conditions. The best solution is a tightly sealed container, such as a "perky box" or a display case with a lid. It is advisable to place a moisture-absorbing agent, such as silica gel, in the container to ensure a stable, dry environment.

Sources

IMA Mineral List (CNMNC)