Quintinite-3T

Chemical formula: Mg₄Al₂(OH)₁₂CO₃·4H₂O

Quintinite-3T is a rare mineral from the hydrotalcite group, forming small, hexagonal, tabular crystals with a vitreous or pearly luster.

## Characteristics Quintinite-3T is a hydrated magnesium aluminum carbonate, belonging to the hydrotalcite supergroup. It forms very small, tabular crystals with a hexagonal outline, rarely exceeding 1 mm in size. It occurs as individual crystals, rosette-like aggregates, or as coatings and efflorescences on other minerals. It is polymorphic with quintinite-2H, meaning it has the same chemical composition but a different crystal structure. ## Physical Properties This mineral is characterized by a hardness of about 2 on the Mohs scale, making it very soft. It has perfect cleavage in one direction, parallel to the basal plane of the crystal. Its luster is described as vitreous to pearly, especially visible on cleavage surfaces. It is transparent to translucent. ## Colors and Varieties Quintinite-3T is usually colorless, white, pale yellow, or light brown. Color variations typically result from the presence of minor impurities. No named varieties of this mineral are distinguished. ## History and Name The name "quintinite" is derived from Quintin Wight (b. 1935), a Canadian mineral collector and expert, in recognition of his contributions to mineralogy. The suffix "-3T" refers to its trigonal symmetry (T) and three-layered unit cell (3). The mineral was described in 1997 by George Y. Chao and Joel D. Grice based on material from the type locality in Canada. ## Uses Quintinite-3T has no industrial applications. Its significance is purely scientific and for collectors, as a rare member of the hydrotalcite group.

Properties

Mohs hardness
2
Color
Bright yellow to pale yellow
Luster
Vitreous
Streak
White
Density
2.14
Cleavage
{0001}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Quintinite-3T is difficult to identify without specialized equipment. It is distinguished by very small, hexagonal, tabular crystals with a pearly luster on basal surfaces. A key diagnostic feature is its vigorous reaction with hydrochloric acid. However, final confirmation requires advanced methods such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other minerals from the hydrotalcite group, such as manasseite, sjögrenite, or its polymorph quintinite-2H. Visual distinction from these minerals is practically impossible and requires crystallographic analysis. From micas, such as muscovite, it is distinguished by lower hardness and reaction with acids. ## Crystal Forms Crystals are almost always very small, tabular in habit, with a well-developed base and a hexagonal outline. They often form aggregates in the shape of rosettes or fans, as well as fine coatings and efflorescences.

Geological environment

## Genesis Quintinite-3T is a secondary mineral, formed under low-temperature hydrothermal processes. It forms in vugs and fractures in various rock types. At the type locality (Mont Saint-Hilaire), it occurs in sodalite xenoliths within nepheline syenites. It is also found in serpentinites and skarns. ## Mineral Associations This mineral co-occurs with many other rare minerals. Depending on the locality, it is accompanied by, among others, analcime, natrolite, microcline, aegirine, petersenite-(Ce), sjögrenite, manasseite, as well as minerals from the serpentine and chlorite groups. ## Localities The most important and type locality for quintinite-3T is the Poudrette quarry at Mont Saint-Hilaire in Quebec, Canada, from which the best known specimens originate. Other confirmed occurrences include the Jacupiranga mine in São Paulo (Brazil), the Polino complex in Umbria (Italy), and the Saranovskiy mine in the Urals (Russia).

Rarity

Very rare

For collectors

## Quality Criteria As a mineral occurring mainly in the form of microscopic crystals, quintinite-3T is primarily valued by collectors specializing in "micromount" specimens. The highest-rated specimens are those with sharp, well-formed, transparent crystals with a distinct luster, forming aesthetic groups or rosettes. Association with other rare minerals is also important, as it increases the scientific and aesthetic value of the specimen. ## Popular Localities Undoubtedly, the most sought-after and well-known locality on the collector's market is Mont Saint-Hilaire in Canada. Specimens from this location are considered the global standard for this mineral.

Care and storage

## Cleaning Quintinite-3T specimens are extremely delicate and small. Mechanical cleaning is highly risky. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust. Avoid contact with water, which can affect the mineral's hydrated structure. ## What to Avoid The mineral is very soft and easily scratched or mechanically damaged. Avoid contact with acids, which rapidly dissolve it with the release of carbon dioxide. It should also be protected from high temperatures, which can cause dehydration and structural damage. ## Storage It is recommended to store specimens exclusively in specialized "micromount" boxes, which protect them from physical damage, dust, and sudden changes in humidity. Exposure should be away from direct sunlight and heat sources.

External references

Sources

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