Vertumnite

Chemical formula: Ca₄Al₄Si₄O₆(OH)₂₄·₃H₂O

Vertumnite is a rare, hydrated calcium aluminum silicate, forming colorless or white, hexagonal crystals and radial aggregates.

## Characteristics Vertumnite is a mineral from the silicate group, chemically classified as a hydrated calcium aluminum silicate. It occurs as small, tabular or platy crystals with a hexagonal outline, which often form radial, spherical aggregates, rosettes, or coatings. Individual crystals rarely exceed 1 mm in size. It is a colorless or white mineral, with a vitreous luster, and a pearly luster on cleavage surfaces. ## Physical Properties This mineral is characterized by low hardness, approximately 2.5 on the Mohs scale. It is brittle and has excellent cleavage in one direction, which accounts for its pearly luster on fracture planes. Its density is approximately 2.33 g/cm³. It is transparent to translucent. ## History and Name Vertumnite was first described in 1977 by Enzo Passaglia and his team. The mineral's name comes from the Etruscan deity Vertumnus (or Voltumna), whose sanctuary was located near Orvieto, not far from the mineral's discovery site (type locality: Campomorto mine in Italy).

Properties

Mohs hardness: 5
Color: Colourless, green
Luster: Vitreous, Pearly
Streak: White
Density: 2.15
Cleavage: Perfect on {0001}
Fracture: Conchoidal
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Vertumnite can be identified by its characteristic, radial aggregates composed of small, hexagonal, tabular crystals. Its white color, pearly luster on cleavage surfaces, and low hardness are key identifying features. It often occurs in cavities and fissures in volcanic rocks. ## Distinguishing from similar minerals It can be confused with other white zeolite-like minerals or silicates found in similar environments, such as tobermorite, thomsonite, or chabazite. Distinguishing it from these minerals often requires advanced analytical methods, such as X-ray diffraction (XRD), due to the small crystal size and visual similarity. ## Crystal forms It forms thin, tabular crystals with a hexagonal outline. These crystals almost always occur as radial, spherical, or hemispherical aggregates and rosettes.

Geological environment

## Genesis Vertumnite is a secondary mineral, formed by low-temperature hydrothermal processes. It forms in cavities, fissures, and geodes in volcanic rocks, such as basalts and tephrites, often altered by weathering processes or hydrothermal activity. ## Mineral associations This mineral co-occurs with other secondary minerals typical of gas vesicles in volcanic rocks. The most common associations include: tobermorite, apophyllite, chabazite, phillipsite, gismondine, calcite, and various minerals from the zeolite group. ## Localities The most important and classic occurrences of vertumnite are in Italy, at the type locality in the Campomorto mine near Montalto di Castro (Viterbo Province) and in the Somma-Vesuvius volcanic complex area. It is also known from Okayama Prefecture in Japan and several localities in Germany (e.g., in the Eifel mountains).

Rarity

Rare

For collectors

## Quality criteria The most valued by collectors are specimens with well-formed, spherical or hemispherical aggregates with a silky or pearly luster. Contrast with the rock matrix and the absence of damage to delicate structures are important. The size of the aggregates, their completeness, and aesthetic arrangement on the host rock significantly increase the specimen's value. ## Popular localities Specimens from the type locality in Italy (Campomorto) and from Japan (Fuka) are considered classic and most desired by collectors specializing in rare minerals or secondary minerals from volcanic zones.

Care and storage

## Cleaning Vertumnite specimens should only be cleaned very carefully, using a soft brush to remove dust. Due to its low hardness and excellent cleavage, ultrasonic cleaners and mechanical cleaning should be avoided. Contact with water should be kept to a minimum. ## What to avoid Contact with acids and other chemicals that can damage the mineral should be avoided. It is sensitive to high temperatures, which can lead to its dehydration and destruction of its structure. It should be protected from scratching by harder minerals. ## Storage Vertumnite specimens are best stored in separate, padded boxes or display cases to prevent mechanical damage and contact with other minerals. They should be protected from dust and direct sunlight.

External references

https://www.mindat.org/min-4174.html