Barringtonite

Chemical formula: MgCO<sub>3</sub>·2H<sub>2</sub>O

Barringtonite is a rare, hydrated magnesium carbonate, forming tiny, colorless or white crystals and coatings.

## Characteristics Barringtonite is a hydrated magnesium carbonate, closely related to nesquehonite. It occurs as very small, bladed or acicular crystals, rarely exceeding 1 mm in length. These crystals often form radial aggregates, rosettes, or thin coatings and crusts on rock surfaces. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties This mineral is characterized by low hardness, 2.5 on the Mohs scale, which means it is very soft and easily scratched. It has a vitreous luster. It is a light mineral, with a density of approximately 2.82 g/cm³. Crystals are usually transparent to translucent. ## Colors and Varieties Barringtonite is most often colorless or white. No colored or commercial varieties are distinguished. ## History and Name The mineral's name comes from its discovery locality in the Barrington Tops quarry, New South Wales, Australia. It was described and approved as a new mineral by the International Mineralogical Association (IMA) in 1963. Its discovery was associated with studies of low-temperature hydrothermal processes in basaltic rocks. ## Uses Barringtonite has no industrial application. Its significance is purely scientific and collectible, as a rare and well-defined mineral species.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
White
Density
2.82
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification Field identification of barringtonite is practically impossible due to its rarity and small crystal size. In a collection, it is recognized by its characteristic, tiny, bladed crystals forming radial aggregates. It reacts vigorously with hydrochloric acid. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Barringtonite is visually almost identical to nesquehonite (MgCO₃·3H₂O), with which it often co-occurs. Nesquehonite usually forms larger crystals. Distinguishing these two minerals without specialized equipment is impossible. It can also be confused with other secondary, white carbonate or sulfate minerals, but its specific crystal form and genesis are helpful in narrowing down the possibilities. ## Crystal Forms Barringtonite crystals are small, bladed or acicular. They usually occur as radial aggregates, rosettes, and also form thin crusts and coatings.

Geological environment

## Genesis Barringtonite is a low-temperature mineral, formed by hydrothermal processes or weathering of magnesium-rich rocks, especially serpentinites and basalts. It forms in fractures and gas vesicles (geodes) in volcanic rocks, where it crystallizes from aqueous solutions at temperatures below 12°C. It is an unstable mineral and at higher temperatures or lower humidity, it transforms into nesquehonite. ## Mineral Associations It most commonly co-occurs with nesquehonite, aragonite, hydromagnesite, and calcite. ## Localities The most important and classic locality, from which the best-formed specimens originate, is Barrington Tops in New South Wales (Australia). This mineral has also been confirmed in several other places worldwide, including Asbestos in Quebec (Canada) and in some Alpine rock fissures, but these occurrences are of much lesser significance.

Rarity

Very rare

For collectors

## Quality Criteria The collectibility of barringtonite primarily depends on the presence of well-formed, aesthetically pleasing crystal aggregates, such as rosettes, visible under magnification. Due to its rarity, every analytically confirmed specimen has value for specialized collectors. Contrast with a dark matrix rock (e.g., basalt) enhances the visual appeal of the specimen. ## Popular Localities The only source of collectible specimens is the type locality – Barrington Tops in Australia. Specimens from other locations are usually microscopic and primarily of scientific interest.

Care and storage

## Cleaning Barringtonite specimens are extremely delicate and sensitive. They should only be cleaned very carefully, using compressed air to remove dust. Any contact with water, even distilled, can cause dissolution or chemical alteration of the mineral. Using brushes is not recommended due to its low hardness. ## What to Avoid Absolute avoidance of contact with water and all chemicals, including acids, which cause its rapid dissolution with the release of carbon dioxide, is necessary. The mineral is unstable in dry air – it can lose water and transform into nesquehonite. It should be protected from high temperatures and direct sunlight. ## Storage It is recommended to store specimens in sealed, transparent containers (so-called "perky boxes") that protect against mechanical damage, dust, and humidity fluctuations. Display should be in stable room conditions, away from heat sources and light.

External references

Sources

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