Fluorstrophite

Chemical formula: SrCaSr₃(PO₄)₃F

Fluorstrophite is a rare strontium and calcium phosphate from the belovite group, forming transparent, greenish or yellowish-green crystals.

## Characteristics Fluorstrophite is a mineral belonging to the belovite group, a rare strontium and calcium phosphate. It occurs as hexagonal, prismatic crystals, which can be elongated or short and tabular. Specimens are usually small but well-formed. This mineral is transparent to translucent, with a vitreous luster. ## Physical Properties Its Mohs hardness is 5, which places it on par with apatite. It has a vitreous luster. It is a relatively brittle mineral. ## Colors and Varieties Fluorstrophite most often takes on a green to yellowish-green color; colorless specimens are also found. No distinct commercial or colored varieties have been identified. ## History and Name The mineral's name refers to its chemical composition – the presence of fluorine (Fluor) and strontium (strophite). It was described and approved as a new mineral species relatively recently. Its type locality is the Inagli chromodiopside deposit in Siberia, Russia. ## Applications Fluorstrophite has no industrial application. Its significance is purely scientific and collectible due to its rarity and the attractive appearance of well-formed crystals.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: White
Density: 0
Transparency: Transparent,Translucent
Crystal system: Hexagonal

Diagnostic features

## Identification Fluorstrophite can be identified by its hexagonal, prismatic crystals, characteristic greenish color, and vitreous luster. A Mohs hardness of 5 is a helpful indicator. Its occurrence in a specific geological environment (alkaline massifs) is also a diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with apatite, which also crystallizes in the hexagonal system and has similar hardness. However, fluorstrophite differs in its chemical composition (high strontium content) and often a more intense, greenish color. Definitive differentiation requires advanced chemical analyses (EDS) or X-ray diffraction (XRD). ## Crystal Forms It forms well-developed, hexagonal crystals with a prismatic habit, often terminated by a pyramid or pinacoid. It also occurs as granular aggregates or radial aggregates.

Geological environment

## Genesis Fluorstrophite is a mineral of magmatic origin, crystallizing in the late stages of nepheline syenite pegmatite formation and in carbonatites. It forms in an environment rich in phosphorus, fluorine, and rare earth elements, including strontium. ## Mineral Associations It often co-occurs with minerals such as microcline, nepheline, aegirine, eudialyte, lorenzenite, lamprophyllite, as well as other phosphates from the apatite and belovite groups. ## Localities The most important and type locality is the Inagli chromodiopside deposit in the Inagli massif, Aldan Shield (Sakha Republic, Russia). It is also known from other alkaline massifs worldwide, for example, the Ilímaussaq complex in Greenland and the Khibiny massif on the Kola Peninsula in Russia.

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp, and undamaged crystals of distinct, prismatic form are most valued by collectors. Intense, green or yellowish-green color and transparency are highly appreciated. The attractiveness of a specimen is also enhanced by its placement on a contrasting rock matrix, in association with other rare minerals. ## Popular Localities By far the most sought-after and classic specimens come from the type locality – the Inagli deposit in Russia. Specimens from the Kola Peninsula (Khibiny massif) are also valued in specialized collections.

Care and storage

## Cleaning Fluorstrophite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, and then the specimen should be thoroughly dried. Ultrasonic cleaners should be avoided, as they can cause cracks. ## What to Avoid This mineral is sensitive to strong acids. Rapid temperature changes and prolonged exposure to direct sunlight, which theoretically can affect its color, should be avoided. Protect from impacts and scratching by harder minerals. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to avoid contact with other minerals that could scratch them. It is good to keep them in stable conditions, away from moisture and heat sources.

External references

https://www.mindat.org/min-3757.html