Nesquehonite

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

Nesquehonite is a hydrated magnesium carbonate, forming characteristic, radially arranged, acicular crystals, often as efflorescences and coatings.

## Characteristics Nesquehonite is a hydrated magnesium carbonate that most often occurs as acicular or fibrous aggregates. It forms radial aggregates, rosettes, as well as crusts and coatings. Well-formed, single crystals are rare and take the form of elongated prisms or needles. It is usually white or colorless. It is a secondary mineral, formed as a result of the weathering of magnesium-rich rocks. ## Physical Properties Nesquehonite is a relatively soft mineral, with a hardness of 2.5 on the Mohs scale. Its crystals exhibit a vitreous luster, while fibrous aggregates show a silky luster. It is transparent to translucent. The mineral's density is approximately 1.83-1.85 g/cm³, making it relatively light. ## Colors and Varieties This mineral is most often colorless or white. Sometimes it is slightly yellowish or grayish due to impurities. There are no named color or commercial varieties. ## History and Name The name nesquehonite comes from its discovery site in 1878 – the Nesquehoning coal mine in the Nesquehoning Valley, Carbon County, Pennsylvania, USA. It was described by F.A. Genth and S.L. Penfield. The mineral was initially found as white efflorescences on mine walls. ## Uses Nesquehonite has no significant industrial application. However, it is valued by mineral collectors for its delicate, acicular forms and interesting origin.

Properties

Mohs hardness
2.5
Luster
Vitreous, Silky
Streak
White
Density
1.83-1.85
Cleavage
Perfect on {110}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Nesquehonite can be identified by its characteristic, radial aggregates of white, acicular crystals. It is very soft and light. A diagnostic feature is its vigorous reaction with hydrochloric acid, during which carbon dioxide is released. Its occurrence as efflorescences in mines or on serpentinites is also an important clue. ## Distinguishing from Similar Minerals It can be confused with other secondary carbonate or sulfate minerals forming efflorescences, such as artinite, hydromagnesite, or epsomite. Artinite forms similar acicular aggregates but crystallizes in the monoclinic system and has slightly different properties. Hydromagnesite more often occurs in crusty or earthy aggregates. Epsomite (Epsom salt) is water-soluble and has a characteristic bitter taste. ## Crystal Forms Nesquehonite crystals are prismatic, elongated, and often striated along the vertical axis. They usually occur as radial or stellate aggregates, as well as in fibrous aggregates, crusts, and as coatings.

Geological environment

## Genesis Nesquehonite is a secondary mineral. It forms at low temperatures as a result of the weathering of ultramafic rocks, such as serpentinites and peridotites, where carbon dioxide-rich waters react with magnesium minerals (e.g., olivine, serpentine). It also forms as an evaporation product of magnesium-rich waters and as efflorescences on mine walls and in caves. ## Mineral Associations It often co-occurs with other magnesium carbonates, such as hydromagnesite, artinite, dypingite, and lansfordite. In serpentinites, it is also accompanied by brucite, olivine, and minerals from the serpentine group. ## Localities The most important localities worldwide include the Nesquehoning Valley in Pennsylvania (USA), from which the mineral's name originates. It also occurs in the Kraubath area in Austria, in the Aosta Valley and Val Malenco in Italy, in the Orenburg Oblast in Russia, and in British Columbia in Canada.

Rarity

Not very common

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, large, and sharp crystals forming aesthetic, radial aggregates. Purity (snow-white color) and the absence of damage to the delicate needles are important. A contrasting matrix, such as dark serpentinite, significantly enhances the visual appeal of the specimen. ## Popular Localities Classic and valued specimens come from the type locality in Pennsylvania, USA. Very good quality material, including large crystal groups, is supplied by Italian deposits, especially in the Aosta Valley and Val Malenco. Specimens from these locations are often sought after by collectors.

Care and storage

## Cleaning Nesquehonite specimens are very delicate and sensitive to water. They should only be dry-cleaned, using a soft brush or compressed air from a safe distance to remove dust. Contact with water can lead to dissolution or damage of the delicate crystals. ## What to Avoid Contact with water, acids, and other chemicals should be strictly avoided. The mineral is sensitive to elevated temperatures, which can cause dehydration and disintegration. It should be protected from direct sunlight and high humidity. ## Storage It is recommended to store specimens in closed, dry containers or display cases to protect them from dust, humidity, and mechanical damage. Due to its fragility, it should be kept away from minerals of greater hardness.

External references

Sources

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