Matteuccite

Chemical formula: NaHS⁶⁺O₄(H₂O)

Matteuccite is a rare, water-soluble sodium sulfate, forming tiny, colorless crystals and efflorescences in volcanic environments.

## Characteristics Matteuccite is a hydrated sodium bisulfate. It occurs as very small, tabular or prismatic crystals, rarely exceeding 1 mm in length. It also forms granular aggregates, powdery efflorescences, and crusts. It is a colorless and transparent mineral with a vitreous luster. Due to its water solubility, it is unstable in humid environments. ## Physical Properties Matteuccite crystals are very soft and brittle. The mineral is characterized by low hardness, estimated at about 2 on the Mohs scale. It has a density close to 2.33 g/cm³. The luster is typically vitreous. ## History and Name The mineral was named in honor of the Italian physicist and neurophysiologist Carlo Matteucci (1811-1868). It was first discovered and described in 1977 by G. Carobbi and C. Cipriani based on samples from fumaroles on Mount Vesuvius in Italy. ## Uses Matteuccite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals or minerals from specific localities, such as Vesuvius.

Properties

Mohs hardness
2
Color
colorless
Luster
Vitreous
Streak
White
Density
2.118
Cleavage
Good on {100}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification A key diagnostic feature is its immediate solubility in water. It is also recognized by its occurrence as small, colorless crystals in the form of efflorescences and crusts in active volcanic environments (fumaroles). ## Distinguishing from Similar Minerals It can be confused with other soluble sulfates found in similar environments, such as thenardite (Na₂SO₄) or mirabilite (Na₂SO₄·10H₂O). Differentiation requires precise analytical methods, such as X-ray diffraction (XRD), although matteuccite crystallizes in a different system (monoclinic) than orthorhombic thenardite. ## Crystal Forms It forms very small, flattened, tabular crystals with hexagonal outlines or elongated, prismatic ones. Most commonly, it is found in the form of loose aggregates, powdery efflorescences, or brittle crusts on volcanic rocks.

Geological environment

## Genesis Matteuccite is a mineral of fumarolic origin. It forms as a result of direct sublimation from volcanic gases or in the reaction of these gases with volcanic rocks at temperatures ranging from 100 to 200°C. It is a product of volcanic activity. ## Mineral Associations It most often co-occurs with other fumarolic minerals, such as thenardite, metathenardite, aphthitalite, and also native sulfur. ## Localities This is a very rare mineral, known from only a few locations worldwide. The type locality is the fumaroles on Mount Vesuvius in Italy. It has also been reported on Mount Etna (Sicily, Italy) and in the Tolbachik volcanic complex in Kamchatka, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The collecting appeal of a specimen depends on the presence of well-formed, even if microscopic, crystals. Samples with distinct, transparent crystals on a contrasting rock matrix are most valued. Due to its rarity, even rich efflorescences and crusts have value for specialized collectors. ## Popular Localities The most classic and desirable specimens come from the type locality – from historical eruptions of Vesuvius in Italy.

Care and storage

## Cleaning The mineral is water-soluble, so it must absolutely not be cleaned with water. To remove dust, a very soft brush or compressed air from a safe distance can be used very carefully. ## What to Avoid Avoid all contact with water, water vapor, and high humidity, which can cause the specimen to dissolve and be destroyed. Protect from all chemicals and sudden temperature changes. ## Storage Matteuccite specimens must be stored in airtight, dry containers, preferably with a desiccant (e.g., silica gel). They should only be displayed in sealed display cases with controlled humidity.

External references

Sources

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