Latiumite

Chemical formula: (Ca,K)<sub>4</sub>(Si,Al)<sub>5</sub>O<sub>11</sub>(S<sup>6+</sup>O<sub>4</sub>,CO<sub>3</sub>)

Latiumite is a rare potassium calcium silicate, distinguished by its pale blue color and occurrence in volcanic products in the Italian region of Latium.

## Characteristics Latiumite is a rare mineral belonging to the silicate group. It forms small, tabular crystals, often aggregated into lamellae or rosette-like clusters. It typically occurs as inclusions within the host rock. It is a brittle mineral. ## Physical Properties Its Mohs hardness ranges from 5.5 to 6. It exhibits a vitreous luster, sometimes greasy on fracture surfaces. It is transparent to translucent. The mineral's density is approximately 2.94 g/cm³. ## Colors and Varieties It is most commonly colorless, white, or pale blue. The blue coloration is most prized by collectors. No commercial varieties are distinguished. ## History and Name The mineral was first described in 1951 by Carlo Lauro. Its name is derived from the Latium region of Italy, where its type locality, the Alban Hills volcanic complex, is situated. ## Uses Latiumite has no industrial applications. It is valued solely as a collector's mineral due to its rarity, attractive appearance, and classic occurrence.

Properties

Mohs hardness
5.5-6
Luster
Vitreous to greasy
Streak
White
Density
2.94
Cleavage
Perfect on {001}, good on {110}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of latiumite include its tabular crystal habit, pale blue color, perfect cleavage in one direction, and specific environment of occurrence. It is found in druses and small cavities in volcanic rocks. ## Distinguishing from Similar Minerals Latiumite is sometimes confused with other pale blue minerals from volcanic environments, such as some feldspars or celestine. It differs from feldspars by its lower hardness and crystal habit. It differs from celestine by its hardness (celestine is significantly softer, about 3-3.5 on the Mohs scale) and lack of reaction with acids. ## Crystal Forms It crystallizes in the monoclinic system, forming thin to thick tabular crystals with a pseudohexagonal outline. It often forms aggregates composed of parallel or radially arranged lamellae.

Geological environment

## Genesis Latiumite is a product of high-temperature, low-pressure contact metamorphism. It forms in lavas and volcanic blocks ejected during eruptions, in the so-called sanidinite facies. ## Mineral Associations It commonly co-occurs with minerals such as sanidine, diopside, leucite, nepheline, andradite, haüyne, vesuvianite, and melilite. ## Localities The most important and classic locality for latiumite is the Alban Hills (Colli Albani) volcanic complex in Latium, Italy. It is also found in the Eifel mountains in Germany, for example, in the Laacher See area and on the Bellerberg volcano.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized latiumite specimens feature well-formed, sharp crystals with an intense blue color. The size of the crystals and their aesthetic arrangement on a contrasting rock matrix are also of great importance. Specimens from the type locality (Alban Hills) are particularly sought after. ## Popular Localities By far the most valued specimens come from Italy, from the Alban Hills region. Good quality collector material is also provided by some localities in the German Eifel mountains.

Care and storage

## Cleaning Latiumite specimens should be cleaned very carefully, using a soft brush and distilled water. Due to its perfect cleavage, it is sensitive to impact and pressure. Ultrasonic cleaners are not recommended. ## What to Avoid Contact with strong acids and other chemicals should be avoided. The mineral is relatively hard, but it should be protected from scratching by harder minerals such as quartz or corundum. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to prevent mechanical damage and contact with dust. Protection from direct, prolonged sunlight is good practice, although the mineral is not particularly light-sensitive.

Sources

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