Dorfmanite

Chemical formula: Na<sub>2</sub>(PO<sub>3</sub>OH)·2H<sub>2</sub>O

Dorfmanite is a rare, water-soluble sodium phosphate, forming white, earthy coatings and brittle aggregates in ultra-alkaline pegmatites.

## Characteristics Dorfmanite is a hydrated acidic sodium phosphate, most commonly found as porous, earthy, or chalky aggregates and coatings. It also forms brittle, fibrous, or platy aggregates. Due to its nature, well-formed crystals are extremely rare and microscopic, usually less than 1 mm. It is a secondary mineral, formed by hydrothermal processes or the weathering of other phosphate minerals in a specific, strongly alkaline environment. ## Physical Properties This mineral is very soft and brittle. It is characterized by low density, comparable to that of ice. It has a vitreous or dull, earthy luster. It is transparent to translucent. One of its key and unusual characteristics for a mineral is its complete solubility in water. ## Colors and Varieties Dorfmanite is usually colorless or white. No colored or commercial varieties are distinguished. ## History and Name The mineral was first described in 1980 by Y. P. Kapustin, Z. V. Pudovkina, and L. N. Khomyakov. The name dorfmanite honors Moisei Davidovich Dorfman (1908–2006), a Russian mineralogist from the Fersman Mineralogical Museum in Moscow, for his contributions to the study of minerals from alkaline massifs. ## Uses Due to its rarity, small size, and instability (water solubility), dorfmanite has no industrial application. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness
1-1.5
Luster
Vitreous
Streak
White
Density
1.89
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification A key diagnostic feature of dorfmanite is its complete solubility in water. In field conditions and collections, it can be recognized by its white color, earthy or fibrous aggregates, and occurrence in paragenesis with other rare alkaline minerals. It is very soft and brittle to the touch. ## Distinguishing from Similar Minerals Dorfmanite can be confused with other secondary, white phosphates or carbonates found in similar environments, such as nahcolite, trona, or thermonatrite. The water solubility test is the simplest way to distinguish it from most similar minerals. Unlike carbonates (e.g., nahcolite), dorfmanite does not react with hydrochloric acid. ## Crystal Forms Well-formed crystals are extremely rare, microscopic, and take the form of thin, platy or acicular crystals. It typically forms earthy, chalky, porous masses or delicate, fibrous aggregates.

Geological environment

## Genesis Dorfmanite is a secondary mineral, formed in the late stages of hydrothermal processes or as a result of weathering within highly differentiated, ultra-alkaline pegmatites and nepheline syenite massifs. It forms in vugs and fissures, often as an alteration product of other, earlier phosphate minerals (e.g., lomonosovite) or as a direct precipitate from residual solutions rich in sodium and phosphorus. ## Mineral Associations This mineral coexists with other rare minerals typical of alkaline pegmatites. Its most common associations include: natrite, thermonatrite, natrophosphate, villiaumite, lomonosovite, aegirine, microcline, nepheline, sodalite, and eudialyte. ## Localities The most important and classic dorfmanite localities are in Russia, on the Kola Peninsula, within the Khibiny and Lovozero alkaline massifs (e.g., Karniurt, Koashva, Rasvumchorr mountains). It has also been identified in the Mont Saint-Hilaire igneous complex in Quebec, Canada, which is another world-class locality for rare minerals.

Rarity

Very rare

For collectors

## Quality Criteria For dorfmanite, due to its nature, the main criterion for value is the abundance and purity of the material on the rock matrix. The most desirable specimens are those with visible, even microscopic, crystalline forms (plates, needles), which are extremely rare. Rich, fibrous aggregates or thick coatings are also highly valued, especially when accompanied by other rare, well-formed associated minerals that create an aesthetic composition. ## Popular Localities By far the most prized and classic dorfmanite specimens come from the alkaline massifs of the Kola Peninsula in Russia, especially from the Khibiny Massif. Specimens from Mont Saint-Hilaire in Canada are also sought after by collectors specializing in this locality.

Care and storage

## Cleaning **Absolutely do not clean dorfmanite with water or any liquids**, as it completely dissolves in them. The only safe method for dust removal is to use a soft, dry brush or gentle compressed air from a distance. ## What to Avoid Avoid contact with water, water vapor, and any chemical solutions. The mineral is hygroscopic, meaning it absorbs moisture from the air, which can lead to its slow degradation. Protect it from high humidity, sudden temperature changes, and direct sunlight, which can cause dehydration. ## Storage Dorfmanite specimens must be stored in conditions of controlled, low humidity. The best solution is a sealed container (e.g., a "perky box") with a desiccant (silica gel). It should be displayed away from sources of moisture and heat.

Sources

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