Girvasite

Chemical formula: NaCa<sub>2</sub>Mg<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub>(CO<sub>3</sub>)(H<sub>2</sub>O)<sub>6</sub>

Girvasite is a rare, hydrated sodium, calcium, and magnesium phosphate, forming small, colorless to white, bladed crystals.

## Characteristics Girvasite is a complex, hydrated phosphate with an additional carbonate group, belonging to the rare minerals. It occurs as very small, bladed or acicular crystals, which rarely exceed 1 mm in length. These crystals often form radial or tangled aggregates, as well as rosette-like clusters. Due to its small size, its visual features are difficult to observe without magnification. ## Physical Properties The mineral is characterized by a hardness of approximately 4 on the Mohs scale. It has a vitreous luster and is transparent to translucent. The density of girvasite is about 2.61 g/cm³. ## Colors and Varieties Girvasite is typically colorless or white. No colored or commercial varieties have been identified. ## History and Name The mineral's name comes from its discovery locality in the Girvas (Гирвас) region in Karelia, Russia. It was first described in 1991 by A.P. Khomyakov, V.I. Stepanov, E.I. Semenov, A.A. Voronkov, and Y.S. Polezhaeva. It was approved by the International Mineralogical Association (IMA) in 1990. ## Applications Girvasite has no industrial applications. Its significance is purely scientific and as a collector's item, as a rare and interesting mineralogical species.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
White
Density
2.61
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of girvasite is practically impossible due to its rarity and small crystal size. Identification requires advanced analytical methods such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). Visually, it can be suspected if small, bladed, colorless crystals are found in a characteristic geological environment. ## Distinguishing from Similar Minerals It can be confused with other rare phosphates or carbonates occurring in similar parageneses, such as some zeolites, bobierrite, or nasturan. Definitive differentiation is only possible based on laboratory analysis. ## Crystal Forms Girvasite forms elongated, bladed or acicular crystals, often flattened. These crystals combine into radial aggregates, rosettes, or chaotic, tangled, felt-like clusters.

Geological environment

## Genesis Girvasite is a hydrothermal mineral. It forms in the late stages of crystallization in veins cutting iron-titanium-vanadium ore deposits, associated with alkaline rock and gabbroid massifs. It forms in cavities and fissures within these rocks. ## Mineral Associations This mineral co-occurs with minerals such as: cancrinite, natrolite, pekovite, bobierrite, pyrite, sphalerite, galena, chalcopyrite, ilmenite, titanite, apatite, calcite, and dolomite. ## Localities The most important and type locality for girvasite is the ore deposit in the Girvas region, near the Girvas volcano, south of Lake Piale-ozero in Karelia, Russia. This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The quality of girvasite specimens is primarily assessed based on the richness and visibility of crystals on the rock matrix. Specimens with well-formed, abundant radial aggregates or rosettes, contrasting with the host rock, are most valued. Due to the microscopic nature of the mineral, the size of individual crystals is not a key criterion; overall aesthetics and abundance of clusters are important. ## Popular Localities The only source of collector specimens is the type locality – the deposit in the Girvas region of Russian Karelia. All specimens available on the market originate from this single location.

Care and storage

## Cleaning Girvasite specimens should be cleaned with the utmost care, using a soft brush to remove dust. Due to its potential reactivity and small crystal size, contact with water and any chemical agents should be avoided. ## What to Avoid Ultrasonic cleaners, acids, detergents, and sudden temperature changes should be avoided. As a mineral containing a carbonate group, it is susceptible to reaction with acids. It should also be protected from moisture. ## Storage It is recommended to store specimens in dry conditions, in closed display boxes or mineral cabinets, to protect them from dust, moisture, and mechanical damage. The best way to display it is to place the specimen in a perky box.

Sources

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