Caresite

Chemical formula: Fe²⁺₄Al₂(OH)₁₂CO₃·3H₂O

Caresite is a rare, greenish-black mineral from the quintinite group, known primarily from unique localities in the Canadian province of Quebec.

## Characteristics Caresite is a hydrated iron and aluminum hydroxyl carbonate, belonging to the quintinite group. It forms very small, tabular or platy crystals, rarely exceeding 1 mm in size. It most commonly occurs as rosette-like or spherical aggregates. Its characteristic feature is a deep, greenish-black color. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2. It has a vitreous luster and a density of 2.59 g/cm³. It is transparent, although its dark color can give the impression of opacity in larger aggregates. ## Colors and Varieties Caresite occurs in a uniform, greenish-black color. No color varieties or commercial forms are known. ## History and Name The mineral's name comes from the Canadian mineral collector, Mr. Gilles H. Caresse (born 1941), who first found this mineral. It was described and approved as a new mineral species in 2005 by George Y. Chao and Robert A. Gault. The type localities are the Poudrette quarry at Mont Saint-Hilaire and the Corporation quarry at Mont Royal in Quebec, Canada. ## Uses Due to its rarity and small crystal size, caresite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or minerals from Mont Saint-Hilaire.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
White
Density
2.59
Cleavage
{0001}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Caresite can be identified by its characteristic greenish-black color, tabular crystal habit, and the formation of rosette-like aggregates. Its occurrence is limited to very specific geological environments, which is a key diagnostic clue. Low hardness (2 on the Mohs scale) and a white streak also aid in identification. ## Distinguishing from Similar Minerals It can be confused with other dark minerals from the quintinite or hydrotalcite group, such as charmarite or quintinite. Distinguishing it from these minerals often requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS), especially since they often co-occur in the same localities. ## Crystal Forms Caresite crystals are hexagonal, with a tabular or platy habit. They typically form fan-shaped, rosette-like, or spherical aggregates, composed of many small, overlapping crystals.

Geological environment

## Genesis Caresite is a secondary mineral, formed in the late stages of hydrothermal processes within alkaline nepheline syenite intrusions. It forms in rock cavities and fissures, often in altered xenoliths. ## Mineral Associations This mineral co-occurs with many other rare minerals typical of Mont Saint-Hilaire and Mont Royal. At the type locality, it was found in association with analcime, natrolite, microcline, aegirine, cancrinite, sodalite, charmarite, and quintinite. ## Localities Caresite is an extremely rare mineral, and its occurrence has been confirmed in only two places worldwide, which are also its type localities: - Poudrette quarry at Mont Saint-Hilaire, Quebec, Canada. - Corporation quarry (Forsyth's) at Mont Royal, Montreal, Quebec, Canada.

Rarity

Very rare

For collectors

## Quality Criteria The most valued caresite specimens are those with well-formed, sharp crystals forming aesthetic, rosette-like aggregates. Contrast with the host rock matrix is important. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. Specimen purity and lack of damage are crucial. ## Popular Localities The only sources of caresite specimens are its two type localities in Quebec, Canada. Specimens from the Poudrette quarry at Mont Saint-Hilaire are much better known and more frequently found on the collector's market than those from Mont Royal.

Care and storage

## Cleaning Caresite specimens should be cleaned with the utmost care, using a soft brush to remove dust. Due to its low hardness, any friction should be avoided. If liquid is necessary, distilled water is recommended, followed by very gentle drying with compressed air. ## What to Avoid Avoid contact with acids and other chemicals that can damage the mineral's carbonate structure. Caresite is soft and brittle, so it must be protected from impacts, scratching, and vibrations. Ultrasonic cleaning should not be used. ## Storage Specimens, especially micromounts, should be stored in sealed, padded boxes to protect them from dust and mechanical damage. Avoid exposure to extreme temperature and humidity changes.

External references

Sources

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