Getchellite

Chemical formula: SbAsS₃

Getchellite is a rare arsenic-antimony sulfide, distinguished by its intense, dark red color and characteristic crystal habit.

## Characteristics Getchellite is an arsenic-antimony sulfosalt, prized by collectors for its exceptionally intense, red color. It typically forms aggregates of platy, imperfectly formed crystals, which can be flexible. Its most characteristic feature is a deep, ruby to orange-red color, often with strong internal fire, especially visible in translucent fragments. It occurs as thin plates, platy aggregates, or granular masses. ## Physical Properties This mineral is very soft, with a Mohs hardness of only 1.5-2, meaning it can be scratched with a fingernail. Crystals exhibit perfect cleavage in one direction, contributing to their platy appearance. The luster on cleavage surfaces is pearly to vitreous, and resinous on other surfaces. It is a relatively dense mineral. ## Colors and Varieties Getchellite occurs in shades from dark red and ruby to orange-red. Its streak, the color of the powdered mineral, is orange-red. No named varieties are distinguished, and its collector value is directly related to the intensity and purity of its color. ## History and Name The mineral's name comes from its discovery locality – the Getchell Mine in Humboldt County, Nevada, USA. It was first described in 1965 by B. G. Weiss, who named it after the mine. It is the type locality mineral for this location. ## Uses Getchellite has no industrial application due to its rarity and small accumulations. It is solely a mineral of scientific and collector interest.

Properties

Mohs hardness: 1.5-2
Color: Dark blood red
Luster: Pearly
Streak: Orange-red
Density: 3.92
Cleavage: Perfect on {001}
Fracture: Splintery
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features of getchellite include its unique, ruby-red color, orange-red streak, very low hardness (1.5-2), and perfect cleavage in one direction, which gives it a platy appearance. Crystals are often flexible. ## Distinguishing from Similar Minerals Getchellite can be confused with cinnabar, realgar, or kermesite. - **Cinnabar** is significantly denser and has a bright red streak. - **Realgar** has a similar color and low hardness, but is very unstable in light (quickly decomposes into a yellow powder – pararealgar) and has a different crystal habit. - **Kermesite** forms acicular or hair-like crystals, not the platy aggregates typical of getchellite. ## Crystal Forms Getchellite crystals are monoclinic, but rarely form well-defined, single forms. Most often, they occur as aggregates of thin, platy or tabular crystals, often arranged in a rosette or fan-like manner. It is also found in the form of granular masses.

Geological environment

## Genesis Getchellite is a hydrothermal mineral. It forms at low temperatures in gold and mercury deposits that are rich in arsenic and antimony. It occurs in veins and vugs, often in association with other sulfides and sulfosalts. ## Mineral Associations This mineral co-occurs with minerals such as: realgar, orpiment, stibnite, cinnabar, galkhaite, laffittite, and quartz. ## Localities The most important and classic locality, from which the best specimens originate, is the Getchell Mine in Humboldt County, Nevada, USA. Other known localities include the Zareh Shuran gold deposit in West Azerbaijan Province, Iran, and the Chauvai deposit in southern Kyrgyzstan.

Rarity

Rare

For collectors

## Quality Criteria The most prized getchellite specimens are characterized by an intense, ruby-red color with strong internal reflections. Well-formed, even if partially, crystals forming aesthetic aggregates, rather than just massive groupings, are highly valued. The size of the crystals and the entire specimen, as well as the absence of mechanical damage, which is common due to the mineral's softness, are also important. Contrasting associations with other minerals, e.g., white quartz, can enhance the specimen's attractiveness. ## Popular Localities By far the most sought-after specimens by collectors come from the type locality – the Getchell Mine in Nevada, USA. These are considered the global standard for this mineral. Specimens from Iran (Zareh Shuran) are also present on the market and valued, although they often have a slightly different character.

Care and storage

## Cleaning Extreme caution must be exercised. Getchellite is extremely soft and brittle. Cleaning should be limited to very gently removing dust with a soft brush or a stream of compressed air from a safe distance. Avoid water and any chemical agents. ## What to Avoid The mineral is sensitive to light – prolonged exposure to sunlight can cause it to darken and lose its intense color. Avoid all chemicals, acids, and detergents. Due to its low hardness, it is very susceptible to scratches and mechanical damage. It should not be heated. Due to its arsenic and antimony content, avoid inhaling dust and wash hands after contact with a specimen. ## Storage Getchellite specimens should be stored in closed, padded boxes, away from other minerals that could scratch them. Display should be in a shaded area, protected from dust and direct sunlight.