Acetamide

Chemical formula: CH<sub>3</sub>CONH<sub>2</sub>

Acetamide is a rare organic mineral, forming colorless or white crystals through sublimation on burning coal dumps.

## Characteristics Acetamide is a mineral from the group of organic compounds, recognized by the International Mineralogical Association (IMA). It occurs as small, tabular or prismatic crystals, as well as efflorescences and crusts. It is one of the few examples of a naturally crystallizing organic compound, previously known as a synthetic product. ## Physical Properties It is characterized by exceptional softness, reaching only 1-1.5 on the Mohs scale, meaning it can be scratched with a fingernail. It is very light, with a density of about 1.17 g/cm³. It has a vitreous, sometimes slightly resinous luster, and is transparent to translucent. ## Colors and Varieties It is usually colorless or white. Impurities can give it grayish or yellowish hues. No colored varieties are distinguished. ## History and Name The mineral's name comes directly from its chemical composition – it is an amide of acetic acid. As a mineral, it was identified and described in 1974 by John H. Barnes and William S. Lute based on finds from a burning anthracite culm bank in Shamokin, Pennsylvania, USA. ## Applications Due to its extreme rarity and small crystal sizes, acetamide has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare and organic minerals.

Properties

Mohs hardness
1-1.5
Luster
Vitreous
Streak
White
Density
1.17
Cleavage
Perfect on {0001}
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic feature is its occurrence environment – burning coal dumps. Furthermore, its extreme softness, low density, and water solubility are characteristic. ## Distinguishing from Similar Minerals It can be confused with other fumarolic sublimates, such as salammoniac (ammonium chloride) or sulfur. Salammoniac crystallizes in the isometric system and has a salty taste, while sulfur has a characteristic yellow color and lower hardness. Acetamide is distinguished by its trigonal crystal form and perfect cleavage. ## Crystal Forms It forms hexagonal-looking, tabular or short prismatic crystals. It often occurs as fine-grained aggregates, efflorescences, and crusts on host rocks.

Geological environment

## Genesis It is a fumarolic mineral. It forms by sublimation from hot gases escaping from burning coal (anthracite) dumps. It crystallizes at lower temperatures, on the surface of the dump, away from the main fire source. ## Mineral Associations It co-occurs with other minerals formed under similar conditions, mainly salammoniac, native sulfur, and rare ammonium sulfates, such as mascagnite. ## Locations The most important and well-documented localities worldwide are the type locality in Shamokin, Pennsylvania (USA), the coal mine in Chervonohrad, Ukraine, and dumps near Ronneburg in Thuringia (Germany).

Rarity

Very rare

For collectors

## Quality Criteria For such a rare mineral, the main criterion is its mere presence and confirmed authenticity. Specimens with well-formed, transparent crystals, even if they are millimeter-sized, are most highly valued. The presence on the original host rock and association with other rare minerals from the given locality increase its value. ## Popular Localities Specimens from the type locality – Shamokin, Pennsylvania – are historically the most important and most sought after by collectors specializing in mineral systematics or organic minerals.

Care and storage

## Cleaning It must absolutely not be cleaned with water or any liquids, as it is soluble in them. Only very gentle dust removal with a soft, dry brush or blowing it off with an air blower from a photographic bulb is permissible. ## What to Avoid Avoid contact with water, water vapor, and high humidity. The mineral has a low melting point (approximately 81°C), so it must be protected from heat and direct sunlight. It is very soft and brittle, susceptible to mechanical damage. ## Storage Acetamide specimens require storage in a sealed, airtight container (e.g., a membrane box or a sealed display case) to isolate them from ambient moisture. They should be kept in a cool place, away from heat sources.

External references

Sources

Read more