Quadridavyne

Chemical formula: [(Na,K)₆Cl₂][Ca₂Cl₂][(Si₆Al₆O₂₄)]

Quadridavyne is a rare mineral from the cancrinite group, a complex sodium, potassium, and calcium aluminosilicate, forming hexagonal crystals.

## Characteristics Quadridavyne is a complex aluminosilicate belonging to the cancrinite group, which is part of the feldspathoid family. It forms hexagonal, prismatic crystals that can reach up to 2 cm in length. It typically occurs in colorless or white forms. It is a transparent mineral with a vitreous luster. Its name refers to a unit cell four times larger than that of davyne, another mineral from the same group. ## Physical Properties Quadridavyne is characterized by a hardness of approximately 6 on the Mohs scale. Its density ranges from 2.41-2.43 g/cm³. It has a vitreous luster, and its crystals are usually transparent. It exhibits imperfect cleavage in two directions. ## Colors and Varieties This mineral is most commonly colorless or white. No colored varieties or trade names have been distinguished. ## History and Name Quadridavyne was first described in 1997 by Elena Bonaccorsi, Stefano Merlino, and Pasquale Orlandi. Its name comes from its structural relationship with the mineral davyne (Latin *quadri*- four) and reflects the fact that its unit cell *a* parameter is twice as large, leading to a unit cell volume four times greater compared to davyne. It was approved as a new mineral by the International Mineralogical Association (IMA) in 1996 (IMA1996-042). The type locality is volcanic tuff caves in Sacrofano, north of Rome, Italy. ## Uses Quadridavyne has no industrial applications. It is solely of interest to collectors of rare minerals and scientists studying its complex crystal structure and genesis.

Properties

Mohs hardness
5
Color
Colourless
Luster
Vitreous
Streak
White
Density
2.335
Cleavage
{001} perfect, {110} distinct.
Fracture
Uneven
Transparency
Transparent
Crystal system
Hexagonal

Diagnostic features

## Identification A characteristic feature of quadridavyne is its hexagonal, prismatic crystal habit. Identification is based on the analysis of crystal form, transparency, vitreous luster, and geological context – its occurrence in cavities of volcanic rocks. However, definitive identification requires advanced research methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Quadridavyne is visually almost impossible to distinguish from other minerals of the cancrinite-sodalite group, such as davyne, vishnevite, or cancrinite, without specialized tests. All these minerals form similar hexagonal crystals and occur in similar environments. It can also be confused with some forms of quartz or feldspars, but it differs from them in hardness and environment of occurrence. ## Crystal Forms Quadridavyne crystallizes in the hexagonal system, forming elongated, prismatic crystals with a hexagonal cross-section. Crystals are often terminated by flat pinacoid faces. It occurs as single, well-formed crystals grown on the walls of rock cavities.

Geological environment

## Genesis Quadridavyne is a mineral of hydrothermal or pneumatolytic origin. It forms in the late stages of magma crystallization, in cavities (geodes and druses) within volcanic rocks, such as phonolitic tephrites and tuffs. It crystallizes from hot, alkali- and chlorine-rich volcanic solutions and gases. ## Mineral Associations This mineral co-occurs with other rare minerals typical of this environment. It is most commonly associated with sanidine, leucite, haüyne, biotite, as well as other minerals from the cancrinite group, such as davyne and afghanite. ## Localities The most important and well-documented occurrences of quadridavyne in the world are in Italy. The type locality is a quarry in Sacrofano, in the province of Rome. Other known localities include the Somma-Vesuvius volcanic complex in Campania and the Vulture region in Basilicata. Outside Italy, its presence has also been reported in the Laacher See volcanic complex in the Eifel mountains in Germany.

Rarity

Very rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, and transparent quadridavyne crystals. Crystals of significant size (over 1 cm), which are rare, are highly prized. The aesthetics of the entire rock matrix and the presence of contrasting associated minerals, such as dark biotite, are also important. Undamaged specimens fetch the highest prices. ## Popular Localities By far the most sought-after and classic specimens come from the type locality in Sacrofano, Italy. Specimens from the Somma-Vesuvius complex and the Eifel region in Germany are also valued, although they often have smaller crystals.

Care and storage

## Cleaning Quadridavyne specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, compressed air can be used. Avoid washing in water, especially with detergents, due to the potential solubility and reactivity of some components. ## What to Avoid Avoid contact with acids and other chemicals that may damage the crystal surface. The mineral is sensitive to rapid temperature changes. It should not be heated or exposed to ultrasound. ## Storage Collector specimens of quadridavyne are best stored in closed, stable containers (so-called perky boxes) to protect them from dust, moisture, and mechanical damage. Due to its rarity and delicacy, avoid placing it in areas prone to shocks or falls.

External references

Sources

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