Fluorvesuvianite
Chemical formula: Ca<sub>19</sub>(Al,Mg)<sub>13</sub>(SiO<sub>4</sub>)<sub>10</sub>(Si<sub>2</sub>O<sub>7</sub>)<sub>4</sub>O(F,OH)<sub>9</sub>
Fluorvesuvianite is a rare mineral from the vesuvianite group, characterized by a dominant fluorine content and distinctive prismatic crystals.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous
- Streak
- White
- Density
- 3.43
- Cleavage
- Weak on {001}, {100} and {110}
- Fracture
- Uneven to conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Fluorvesuvianite can be identified by its characteristic crystal habit – long, tetragonal prisms, often terminated by a pyramid. Its brown to reddish-brown color, vitreous luster, and occurrence in metamorphic rocks (skarns) are also important indicators. However, definitive confirmation requires advanced chemical analyses (EDS/WDS) to confirm the dominance of fluorine. ## Distinguishing from Similar Minerals It can be confused with other minerals from the vesuvianite group, from which it is virtually impossible to distinguish visually. It differs from them by its dominant fluorine content. It may also resemble some tourmalines (e.g., dravite) or epidote, but it differs in crystal habit (tourmaline has a trigonal cross-section, and epidote has a monoclinic habit) and hardness. ## Crystal Forms Crystals are tetragonal, prismatic in habit, elongated along the [001] axis. They typically have a square cross-section and are terminated by pyramid faces {111}. They often show striations on the prismatic faces {110} and {100}.
Geological environment
## Genesis Fluorvesuvianite is a mineral typical of magnesian skarns. It forms as a result of contact metamorphism at the interface of magmatic intrusions (e.g., granites) with carbonate rocks (dolomites). It requires an environment rich in calcium, aluminum, silicon, and fluorine. ## Mineral Associations It most commonly co-occurs with minerals such as: calcite, dolomite, diopside, grossular (garnet), spinel, fluorite, phlogopite, as well as other minerals from the vesuvianite group. ## Localities The most important and well-documented localities worldwide include: - Russia: Lupikko mine, Pitkäranta, Karelia – this is the type locality (locus typicus) for this mineral. - Italy: Several localities in the Aosta Valley, including Bellecombe, where it occurs in skarns. - Romania: Ocna de Fier mine in Banat.
Rarity
Very rare
For collectors
## Quality Criteria Specimens with well-formed, sharp, and undamaged crystals of intense, reddish-brown color are most valued by collectors. Transparency and the aesthetic placement of crystals on the rock matrix, especially in association with contrasting minerals such as white calcite, are important. Large crystal sizes (above 1-2 cm) significantly increase the value of a specimen. ## Popular Localities Specimens from the type locality in Lupikko, Russia, are most sought after by collectors specializing in mineral systematics. Good quality crystals also come from Italian and Romanian localities.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Ultrasonic cleaners should be avoided, as they can cause fractures. ## What to Avoid The mineral is sensitive to strong acids, especially hydrofluoric acid. It should be protected from sudden temperature changes and direct, prolonged exposure to sunlight, which can affect its color. Avoid contact with household chemicals. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to prevent scratching by harder minerals. Stable humidity and temperature conditions should be ensured.