Naalasite

Chemical formula: NaAl(As₅+O₃OH)₂·H₂O

Naalasite is an extremely rare sodium and aluminum arsenate, forming colorless, acicular crystals in radial aggregates.

## Characteristics Naalasite is a hydrated sodium and aluminum arsenate, occurring as small aggregates. It forms colorless, transparent crystals with an acicular or thin prismatic habit, which combine into characteristic radial or stellar aggregates. Individual crystals rarely exceed 0.3 mm in length. This mineral is also found as thin crusts on the host rock. ## Physical Properties Naalasite crystals are characterized by a vitreous luster and are transparent. The mineral is brittle. Its Mohs hardness has not yet been determined. The density calculated based on its chemical composition and crystal structure is approximately 3.61 g/cm³. ## Colors and Varieties Naalasite is a colorless mineral. No colored varieties or trade names are known. ## History and Name The name naalasite is derived from its chemical composition – the presence of **Na** (sodium), **al**uminum, and **as**enic. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2021 (IMA2021-022). Its discovery and description were made by a team of mineralogists led by Anthony R. Kampf. ## Uses Due to its extreme rarity and occurrence as microscopic crystals, naalasite has no industrial applications. It is solely an object of scientific and collecting interest.

Properties

Luster: Vitreous
Streak: White
Density: 3.61
Cleavage: None
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification The characteristic feature of naalasite is its radial aggregates composed of colorless, acicular crystals with a vitreous luster. Its identity can be confirmed based on its unique occurrence environment and paragenesis with other rare arsenates and sulfates. ## Distinguishing from Similar Minerals Visually, it can be confused with other colorless, secondary minerals forming acicular aggregates that occur in similar environments (e.g., some sulfates or other arsenates). Definitive identification is only possible using advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Crystal Forms Naalasite crystallizes in acicular to thin, prismatic crystals. Most often, it forms radial, divergent, or stellar aggregates, as well as thin crusts.

Geological environment

## Genesis Naalasite is a secondary mineral, formed in the oxidation zone of polymetallic hydrothermal deposits under desert climate conditions. It is a post-mining mineral, crystallizing directly on the walls of mine workings from acidic, arsenic- and sulfate-rich solutions. ## Mineral Associations This mineral occurs in association with many other rare secondary minerals. Its most common associations include: alunite, antofagastaite, babánekite, cobaltokoritnigite, conichalcite, eriocalcite, lavendulan, magnesiokoritnigite, metazeunerite, parnauite, scorodite, tamarugite, and torrecillasite. ## Localities The only known locality for naalasite in the world is its type locality – the Torrecillas mine in the Salar Grande area, El Tamarugal Province (Tarapacá Region) in Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of naalasite specimens, typically micromounts, is assessed based on several criteria. The abundance and aesthetics of the aggregates are most important – those with well-formed, distinct radial aggregates are most valued. The purity of the crystals and the absence of damage are also significant. Specimens where naalasite coexists with other rare and aesthetic associated minerals are highly rated. ## Popular Localities All known collector specimens come from a single location in the world – the Torrecillas mine in Chile. This is also the type locality for this mineral.

Care and storage

## Cleaning Naalasite specimens are extremely delicate and brittle. For dust removal, only careful use of compressed air from a safe distance is recommended. Any contact with water, especially mechanical cleaning with brushes, risks irreversible damage to the acicular crystals. ## What to Avoid Avoid contact with all chemicals, especially acids. The mineral is sensitive to shocks and impacts. Ultrasonic cleaners must not be used. As a hydrated mineral, it may be sensitive to high temperatures, which can lead to its dehydration and destruction of its structure. ## Storage Collector specimens of naalasite, usually in the form of micromounts, should be stored in sealed, padded boxes that protect them from dust, light, and mechanical damage. Each specimen should be properly labeled.

Sources

IMA Mineral List (CNMNC)