Enricofrancoite

Chemical formula: KNaCaSi<sub>4</sub>O<sub>10</sub>

Enricofrancoite is a rare potassium, sodium, and calcium silicate, forming colorless, tabular crystals with a pearly luster.

## Characteristics Enricofrancoite is a silicate mineral belonging to the rare leifite group. It occurs as very small, colorless, tabular or bladed crystals, typically not exceeding 0.2 mm in length. These crystals often form radial or spherulitic aggregates. Due to their small size, the visual characteristics of the mineral are difficult to observe without a microscope. ## Physical Properties The mineral has a hardness of approximately 6 on the Mohs scale. It exhibits a pearly luster on cleavage surfaces and a vitreous luster on other faces. It is transparent to translucent. The calculated density is 2.63 g/cm³. ## Colors and Varieties Enricofrancoite is colorless. No colored or commercial varieties have been identified. ## History and Name The mineral was discovered in samples from the Vispi quarry in the municipality of San Venanzo (Terni province, Umbria, Italy), which is its type locality. It was approved by the International Mineralogical Association (IMA) in 2021 under number IMA2021-049. The name honors Professor Enrico Franco (1923–2020), an Italian mineralogist from the University of Naples, for his contributions to mineralogical research, including studies of minerals from San Venanzo. ## Uses Enricofrancoite has no industrial or commercial significance. It is solely an object of scientific and collecting interest within micromineral collections.

Properties

Mohs hardness
6
Luster
Pearly
Streak
White
Density
2.63
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of enricofrancoite is practically only possible using advanced analytical methods, such as Raman spectroscopy, X-ray diffraction (XRD), and chemical analysis (EDS/WDS). Visual identification in the field or even in a collection is impossible due to its microscopic size and lack of characteristic macroscopic features. ## Distinguishing from Similar Minerals It can be confused with other colorless, acicular or tabular microminerals found in the same environment, such as other leifites. Definitive differentiation requires specialized laboratory analysis. ## Crystal Forms It forms thin, tabular or bladed crystals, elongated along the [100] axis and flattened parallel to {001}. These crystals often combine into radial or spherulitic (spherical) aggregates.

Geological environment

## Genesis Enricofrancoite forms under volcanic conditions. It has been found in small geodes and vugs within melilitic lavas that interacted with potassium-rich fluids. It is a product of gas-phase or hydrothermal crystallization in the late stage of volcanic activity. ## Mineral Associations At the type locality, it coexists with minerals such as calcite, aragonite, phillipsite, chabazite, willhendersonite, montenaryite, and the newly described sanvenanzoite. ## Localities The only confirmed occurrence of enricofrancoite worldwide is its type locality: the Vispi quarry, located near the San Venanzo volcano in Terni province, Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, enricofrancoite is primarily valued for the richness and quality of crystals on the rock matrix. The most desirable specimens are those with well-formed, sharp, undamaged crystals forming aesthetic, radial aggregates. Association with other rare minerals from this locality is also important. ## Popular Localities The only source of specimens is the Vispi quarry in Italy. Material from this locality is extremely rare and sought after by collectors specializing in microminerals and systematic mineral collections.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the extreme fragility and small size of the crystals, any mechanical contact, including with water or brushes, should be avoided. ## What to Avoid Avoid contact with chemicals, ultrasonic cleaners, and sudden temperature changes. The crystals are very delicate and susceptible to mechanical damage. ## Storage It is recommended to store specimens exclusively in specialized micromineral boxes to protect them from dust, shocks, and damage. Display should only occur under a microscope.

Sources

Read more