Lasmanisite

Chemical formula: Ag₁+₁₂Pb₂+₁₃Mn₂+₁₁Sb₃+₄₄S₂-₉₆

Lasmanisite is an extremely rare sulfosalt of silver, lead, manganese, and antimony, known exclusively from a single locality in Japan.

## Characteristics Lasmanisite is a mineral with a metallic, gray to black color, forming very small, acicular or bladed crystals. They usually occur as tangled or radial aggregates and clusters. Due to the microscopic size of the crystals, its visual features are difficult to observe without specialized equipment. It is an opaque mineral. ## Physical Properties The mineral is characterized by a metallic luster and a black streak. Its Mohs hardness is estimated at 3.5-4. The density calculated based on chemical composition and crystal structure is approximately 5.43 g/cm³. It has good cleavage in one direction. ## Colors and Varieties Lasmanisite occurs in a uniform, metallic-gray or black color. No color or commercial varieties have been distinguished, which is typical for such rare and recently discovered minerals. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2021. Its name honors Raymond Lasmanis, an American geologist and former Washington State Geologist, for his contributions to mineralogy. The type locality (locus typicus) and only known occurrence is the Nakase mine in Japan. ## Applications Lasmanisite has no commercial or industrial applications. Its significance is purely scientific and collectible, being an object of interest for specialized micromineralogists and research institutions.

Properties

Mohs hardness: 3.5-4
Luster: Metallic
Streak: Black
Density: 5.43
Cleavage: Good on {10-10}
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of lasmanisite is impossible based on visual characteristics alone. Due to its microscopic size and similarity to many other sulfosalts, the only reliable method of identification is advanced chemical analysis, such as X-ray microanalysis (EDS/WDS), which allows for the determination of its unique elemental composition. Its occurrence in the only known locality is a key clue. ## Distinguishing from Similar Minerals Lasmanisite can be confused with other gray, metallic sulfosalts occurring in the same environment, such as uchucchacuaite, miargyrite, pyrargyrite, or galena. It differs from them in its precise chemical composition, and its distinction requires specialized laboratory tests. ## Crystal Forms The mineral forms very small, elongated crystals with a bladed or acicular habit. These crystals most often occur as disordered, tangled aggregates or form small clusters with a radial structure.

Geological environment

## Genesis Lasmanisite forms under hydrothermal conditions, in low-temperature, polymetallic epithermal ore veins. It is a product of crystallization from solutions rich in sulfur, antimony, silver, lead, and manganese. ## Mineral Associations This mineral occurs in association with other, more well-known sulfosalts and sulfides. The most common associated minerals at the type locality include: uchucchacuaite, miargyrite, pyrargyrite, galena, sphalerite, and quartz, which is the main gangue mineral. ## Localities The only confirmed and described occurrence of lasmanisite in the world is the Nakase mine, near the city of Yabu, in Hyōgo Prefecture on Honshu Island, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of lasmanisite specimens, being a typical micromineral, is assessed differently than in the case of large crystals. The most important criterion is the richness and clarity of the crystalline aggregates on the rock matrix. Specimens where lasmanisite forms well-developed clusters in association with other rare minerals are highly valued. The certainty of identification confirmed by analysis is also crucial. ## Popular Localities The only source of lasmanisite specimens is its type locality - the Nakase mine in Japan. The mineral is not found anywhere else in the world, making it one of the rarest collector's items.

Care and storage

## Cleaning Lasmanisite specimens are extremely delicate and usually microscopic in size. Cleaning should be kept to an absolute minimum. Only very careful use of a soft brush or blowing off dust with compressed air from a distance and at low pressure is permissible. Avoid contact with water and any chemicals. ## What to Avoid As a complex sulfosalt, the mineral may be sensitive to moisture, oxidation, and acids. Avoid ultrasonic cleaners, sudden temperature changes, and exposure to aggressive chemicals. Prolonged exposure to strong light and humid air can lead to slow decomposition. ## Storage It is recommended to store specimens in a stable, dry environment, preferably in a tightly sealed "micromount" box, protecting them from dust, moisture, and mechanical damage. Store away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)