Lévyne-Ca

Chemical formula: Ca<sub>3</sub>(Si<sub>12</sub>Al<sub>6</sub>)O<sub>36</sub>·18H<sub>2</sub>O

Levyne-Ca is a hydrated calcium aluminosilicate from the zeolite group, forming characteristic, tabular crystals with a hexagonal outline.

## Characteristics Levyne-Ca is a mineral belonging to the zeolite group. It forms thin to thick, tabular crystals with a hexagonal outline, which often occur as twinned aggregates, resembling superimposed, slightly rotated plates. Crystals are usually small, rarely exceeding a few millimeters in diameter. It occurs in vesicles and fissures of volcanic rocks, such as basalts and andesites. ## Physical Properties This mineral is characterized by a hardness of 4-4.5 on the Mohs scale. It has a vitreous luster and is transparent to translucent. Its density is approximately 2.1 g/cm³, which is typical for zeolites. ## Colors and Varieties Levyne-Ca is most commonly colorless or white. It can also take on yellowish, grayish, greenish, or reddish-brown hues, which is associated with the presence of impurities. No named varieties are distinguished. ## History and Name The mineral's name comes from the French mineralogist Armand Lévy (1795-1841). It was first described in 1825. The suffix "-Ca" was added in 1997 by the International Mineralogical Association (IMA) to distinguish it from other members of the levyne series, in which sodium predominates (Levyne-Na). ## Uses Levyne-Ca, like other zeolites, has potential applications as a molecular sieve, catalyst, and in ion exchange processes due to its porous crystal structure. However, due to its rarity, it is not mined for industrial purposes and remains primarily an object of interest for collectors and scientists.

Properties

Mohs hardness
4-4.5
Luster
Vitreous
Streak
White
Density
2.09-2.16
Cleavage
Good on {0001}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic feature of levyne-Ca is its characteristic, tabular crystals with a hexagonal outline, often forming penetration twins. Its occurrence in vesicles in basaltic rocks is also an important clue. ## Distinguishing from Similar Minerals Levyne-Ca is sometimes confused with other zeolites of similar habit, especially chabazite and herschelite. However, chabazite forms crystals with a shape similar to a cube (pseudorhombohedral), rather than flat tablets. Herschelite also forms thin plates, but these are usually grouped into fan-shaped or spherical aggregates. Accurate distinction often requires chemical or crystallographic analysis. ## Crystal Forms Crystals are thin to thick tabular, with a hexagonal outline. They often occur as penetration twins, where six individual crystals are intergrown and rotated relative to each other, forming complex, star-shaped forms. It is also found in the form of radial aggregates or as coatings and crusts.

Geological environment

## Genesis Levyne-Ca is a low-temperature hydrothermal mineral. It forms as a result of the activity of post-magmatic waters or circulating groundwater, which, by passing through aluminosilicate-rich volcanic rocks, leads to the crystallization of the mineral in voids and fissures. It is a typical secondary mineral in amygdaloidal vesicles in basalts, andesites, and other lavas. ## Mineral Associations It most commonly co-occurs with other zeolites, such as chabazite, phillipsite, natrolite, analcime, as well as with calcite and opal. ## Localities Significant specimens come from the Faroe Islands (Denmark), Iceland (e.g., around Djúpivogur), Northern Ireland (County Antrim), Italy (around Vesuvius and Vicenza), Germany (Vogelsberg), and the USA (Oregon, Washington, New Jersey).

Rarity

Not very common

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, and clearly visible crystals with a hexagonal outline. Characteristic penetration twins are particularly sought after. Transparency and lack of damage are highly rated. The attractiveness is also enhanced by a contrasting background of the host rock (matrix) and association with other well-formed minerals, e.g., other zeolites. ## Popular Localities Classic and most prized specimens come from basalts in County Antrim, Northern Ireland, and from Iceland. Specimens from Goble, Oregon (USA) are also known for their good quality crystals.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used. Ultrasonic cleaners should be avoided, as they can damage delicate crystals. ## What to Avoid Contact with acids and other aggressive chemicals should be avoided. As a zeolite, levyne-Ca is sensitive to high temperatures, which can cause the loss of water from its structure (dehydration) and irreversible damage to the crystals. Prolonged exposure to direct sunlight should also be avoided. ## Storage Specimens should be stored in stable conditions, away from heat sources and sudden temperature changes. It is best to place them in a closed display box or cabinet to protect them from dust and mechanical damage.

External references

Sources

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