Laphamite

Chemical formula: As₂Se₃

Laphamite is a rare arsenic selenide, forming aggregates of platy, orange-red crystals with a metallic luster.

## Characteristics Laphamite is a seleno-arsenic mineral with a characteristic, bright color. It occurs as small, platy or bladed crystals, which often form rosette-like or radial aggregates. Its crystals are usually very small, rarely exceeding a millimeter in length. Due to its chemical composition, it is a brittle mineral. ## Physical Properties This mineral is very soft, with a Mohs hardness of 1-2. It has a high refractive index, which, combined with its metallic to submetallic luster, gives it a distinctive appearance. It is opaque. ## Colors and Varieties Laphamite occurs in shades from orange-red to dark red. No varieties have been distinguished. ## History and Name The mineral is named in honor of Davis M. Lapham (1931-1974), a mineralogist and former director of the Pennsylvania Geological Survey. It was first described in 1980 based on material found on a coal mine dump in Burnside, Pennsylvania, USA. ## Uses Laphamite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
1-2
Color
Dark red
Luster
Metallic
Streak
Red-orange
Density
4.5
Cleavage
On {010}
Fracture
Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Laphamite is identified by its characteristic orange-red color, platy crystal habit forming rosette-like aggregates, and occurrence in a specific environment – on coal mine dumps after fires. Its very low hardness is also a diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with realgar (AsS), which has a similar color but usually forms thicker, prismatic crystals and occurs in different geological environments (hydrothermal sources). Laphamite is also much rarer. Distinguishing it from other rare arsenic selenides requires advanced analytical methods. ## Crystal Forms Crystals are platy, flattened parallel to {010}, and often elongated. They form fan-shaped, rosette-like, or spherulitic aggregates, as well as thin coatings and crusts.

Geological environment

## Genesis Laphamite is a secondary mineral, formed by fumarolic processes on burning coal mine dumps. It forms in zones with temperatures ranging from 90 to 150°C through sublimation from arsenic- and selenium-rich gases, which are released during the combustion of sedimentary rocks associated with coal seams. ## Mineral Associations This mineral co-occurs with other sublimation products, such as native sulfur, realgar, orpiment, as well as various rare selenides and sulfides, e.g., downeyite (SeO₂) and sal ammoniac (NH₄Cl). ## Localities The most important and type locality for laphamite is the coal mine dump in Burnside, Northumberland County, Pennsylvania (USA). It has also been identified in other localities with similar genesis, for example, in the Czech Republic (Kladno mine) and in Russia (Chelyabinsk coal basin).

Rarity

Very rare

For collectors

## Quality Criteria The most prized laphamite specimens are those with well-formed, sharp crystals forming aesthetic, rosette-like aggregates. An intense, orange-red color is a key factor. Due to the microscopic size of the crystals, specimens are evaluated under magnification. Contrast with a light matrix enhances visual appeal. ## Popular Localities Undoubtedly, the most classic and sought-after source of laphamite by collectors is its type locality – Burnside, Pennsylvania. Specimens from this location are considered exemplary for this species.

Care and storage

## Cleaning Laphamite specimens are extremely delicate and brittle. Mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust. Avoid contact with water and any chemicals. ## What to Avoid Ultrasonics, steam cleaners, acids, solvents, and detergents should be strictly avoided. The mineral is light-sensitive – prolonged exposure can cause it to darken and degrade. It should be protected from high temperatures and humidity. ## Storage Laphamite specimens should be stored in stable conditions, in closed, padded boxes (e.g., "micromount" type), protected from light, dust, and mechanical damage. Due to its arsenic content, hands should be washed after handling the mineral.

External references

Sources

Read more