Urea

Chemical formula: CO(N³⁻H₂)₂

Urea is a rare, naturally occurring organic mineral, which is the crystalline form of the chemical compound primarily known as a metabolic product.

## Characteristics Urea as a mineral is the natural, crystalline form of the organic compound with the same chemical formula. It typically forms small, prismatic or acicular crystals, often gathered in radial aggregates or crusts. It is a very brittle and soft mineral. Due to its water solubility, it occurs exclusively in extremely dry, desert conditions, where it is protected from precipitation. ## Physical Properties This mineral is characterized by low hardness, approximately 1.5 on the Mohs scale, and low density, about 1.33 g/cm³. It has a vitreous luster and is translucent. Its brittleness makes specimens very delicate. ## Colors and Varieties It is most often colorless, but can take on pale yellow or pale brown coloration, likely due to impurities or inclusions. No named varieties of this mineral are distinguished. ## History and Name The mineral's name comes directly from the name of the chemical compound. As a mineral, it was first described in 1972 based on finds from Toppin Hill in the Laverton Shire region of Western Australia. Its genesis is linked to animal excrement in an extremely arid climate. ## Uses Naturally occurring urea has no industrial application due to its rarity and small accumulations. It is solely an object of collector and scientific interest as one of the few organic minerals.

Properties

Mohs hardness: 1.5
Luster: Vitreous
Streak: yellowish white
Density: 1.33
Cleavage: None
Fracture: Conchoidal
Transparency: Translucent
Crystal system: Tetragonal

Diagnostic features

## Identification The key diagnostic feature of urea is its extreme solubility in water. Low hardness, low density, and occurrence in a specific, dry environment (e.g., in association with guano) are also important indicators. Crystals typically have the form of elongated prisms. ## Distinguishing from Similar Minerals It can be confused with other colorless or white, brittle secondary minerals occurring in similar environments, such as some nitrates (nitratine, niter) or evaporites. The water solubility test is the simplest way to distinguish them. In laboratory conditions, chemical analyses are decisive. ## Crystal Forms Urea crystallizes in the tetragonal system, forming elongated, prismatic or acicular crystals. They often occur as radial aggregates, rosettes, or thin crusts on rock surfaces.

Geological environment

## Genesis Urea is an organic mineral of biogenic origin. It forms as a result of the decomposition of urine (contained in excrement) of bats, birds, or other animals. Its crystallization and preservation in solid form are only possible under conditions of extreme dryness (desert or arid climate), which prevent its dissolution by precipitation or atmospheric moisture. ## Mineral Associations It co-occurs with other minerals formed in similar conditions, mainly related to guano decomposition. Typical associated minerals include phosphammite, weddellite, whitlockite, and various phosphates and sulfates. ## Localities The most important and type locality is Toppin Hill in Laverton Shire, Western Australia. It has also been reported in caves with bat guano in the Al-Kharj region of Saudi Arabia. These are the only confirmed, significant occurrences of this rare mineral.

Rarity

Very rare

For collectors

## Quality Criteria The collector appeal of urea specimens primarily depends on the crystal habit and size. Well-formed, transparent, prismatic crystals are most valued, especially those forming aesthetic, radial aggregates. Association with other rare organic minerals and a well-defined, stable rock matrix are also important. Purity and lack of mechanical damage significantly increase the specimen's value. ## Popular Localities The vast majority, if not all, specimens available on the collector market come from the type locality at Toppin Hill in Western Australia. Specimens from other locations are virtually unheard of in trade.

Care and storage

## Cleaning Urea specimens must absolutely not be cleaned wet. Any contact with water, even a damp cloth, will cause it to dissolve and be destroyed. Only very careful removal of dust with a soft, dry brush or a gentle stream of compressed air from a distance is permissible. ## What to Avoid Avoid water, alcohol, and any other liquids. The mineral is hygroscopic, meaning it absorbs moisture from the air, so it must be protected from high humidity. It is also very soft and brittle, so avoid any impacts, scratches, and pressure. ## Storage Urea specimens require storage in conditions of controlled, low humidity. The best solution is a sealed container (e.g., a "perky box") with a desiccant (e.g., silica gel). It should be displayed away from direct sunlight and heat sources.