Nastrophite

Chemical formula: NaSr(PO₄)(H₂O)₉

Nastrophite is a rare, hydrated sodium strontium phosphate, forming colorless or white, granular aggregates and rare crystals.

## Characteristics Nastrophite is a rare mineral from the phosphate group, chemically classified as a hydrated sodium strontium phosphate. It most commonly occurs as fine-grained, granular, or massive aggregates. It is rarely observed in the form of well-developed, small, regular crystals, reaching up to 1 cm. It is usually colorless to white, sometimes grayish. Due to its rarity and small crystal size, it is primarily an object of interest for collectors specializing in rare minerals. ## Physical Properties This mineral is characterized by a Mohs hardness of approximately 2, making it very soft. It has a vitreous luster on crystal faces and a greasy luster on fractures. It is transparent to translucent. Its density is approximately 2.06 g/cm³. It is brittle and easily susceptible to mechanical damage. ## Colors and Varieties Nastrophite is usually colorless or white. It can take on shades of gray, likely due to impurities or inclusions. No named color varieties or commercial varieties are distinguished. ## History and Name The name "nastrophite" comes from its chemical composition: "Na" (sodium, Latin *natrium*), "stro" (strontium), and "phite" (from "phosphate"). The mineral was first described in 1981 by A.P. Khomyakov, who discovered it in the Khibiny Massif on the Kola Peninsula in Russia. This is its type locality. ## Uses Nastrophite has no industrial application. Its significance is purely scientific and collectible.

Properties

Mohs hardness
2
Color
Colorless
Luster
Vitreous, Greasy
Streak
White
Density
2.05
Cleavage
None
Fracture
Conchoidal
Transparency
Transparent
Crystal system
Isometric

Diagnostic features

## Identification Nastrophite is identified by its occurrence in a characteristic geological environment – alkaline nepheline massifs. Key features include low hardness (around 2), a regular crystallographic system, vitreous luster, and occurrence as granular aggregates or small, cubic crystals. It reacts with acids. ## Distinguishing from Similar Minerals It can be confused with other colorless or white minerals occurring in similar parageneses, such as analcime or natrolite. It is distinguished from them by its lower hardness, regular crystal habit (if visible), and chemical composition, which requires advanced analyses (EDS/XRD) for definitive confirmation. ## Crystal Forms It crystallizes in the isometric system. Most often, it forms granular, massive aggregates. Well-formed crystals are rare and take the form of cubes, sometimes modified by octahedra. Crystals are usually small, not exceeding 1 cm.

Geological environment

## Genesis Nastrophite is a hydrothermal mineral. It forms in the late stages of crystallization in ultra-alkaline, differentiated intrusions, such as nepheline-syenite pegmatites. It crystallizes in vugs and fractures from solutions rich in sodium, strontium, and phosphorus. ## Mineral Associations This mineral co-occurs with other minerals typical of alkaline pegmatites. The most common associations include aegirine, microcline, nepheline, lorenzenite, lomonosovite, villiaumite, analcime, and natrolite. ## Localities The most important and well-documented occurrences of nastrophite worldwide are the ultra-alkaline massifs on the Kola Peninsula in Russia, especially the Khibiny Massif (Koashva mine, Yukspor mountain) and the Lovozero Massif (Alluaiw mountain). These are the places from which the best specimens of this mineral originate. Outside Russia, its presence has been noted in the Pilanesberg alkaline complex in South Africa.

Rarity

Very rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, sharp, and transparent crystals of regular, cubic habit. Rich crystalline aggregates on a contrasting matrix, for example, on dark aegirine, are also highly prized. Crystal size is a key factor – any specimen with crystals exceeding a few millimeters is considered exceptional. Clarity (lack of inclusions) and absence of mechanical damage significantly increase the value of the specimen. ## Popular Localities Undoubtedly, the best and most sought-after nastrophite specimens come from its type locality – the Khibiny Massif on the Kola Peninsula in Russia. Specimens from the Koashva mine are considered the global standard for this mineral.

Care and storage

## Cleaning Nastrophite specimens should be cleaned with the utmost care due to their high softness and brittleness. It is best to use compressed air to remove dust. If wet cleaning is necessary, use only distilled water and a very soft brush, avoiding any scrubbing. After cleaning, the specimen should be immediately and thoroughly dried. ## What to Avoid The mineral is sensitive to acids and other chemicals. Ultrasonic cleaners, which could damage it, should be avoided. As a hydrated mineral, it is sensitive to elevated temperatures, which can lead to dehydration and destruction of its structure. It should be protected from prolonged exposure to moisture. ## Storage Nastrophite specimens should be stored in separate, padded boxes to prevent scratching by harder minerals. It is best to keep it in stable conditions, away from direct sunlight and heat sources.

External references

Sources

Read more