Dalnegorskite

Chemical formula: Ca<sub>5</sub>Mn<sup>2+</sup>(Si<sub>3</sub>O<sub>9</sub>)<sub>2</sub>

Dalnegorskite is a rare calcium and manganese silicate, forming colorless to white, fibrous or bladed crystals.

## Characteristics Dalnegorskite is a mineral from the silicate group, chemically classified as a calcium and manganese silicate. It occurs as colorless to white, transparent aggregates. It typically forms fibrous, bladed, or radial aggregates, composed of elongated crystals reaching up to 1 cm in length. Its name directly refers to its discovery locality. ## Physical Properties This mineral is characterized by a Mohs hardness of 6. It has a vitreous luster and a white streak. It is a relatively light mineral, with a density of approximately 2.83 g/cm³. Crystals exhibit perfect cleavage in one direction. ## History and Name Dalnegorskite was first described in 2020 by Russian mineralogists. Its name comes from the city of Dalnegorsk (Дальнего́рск) in Primorsky Krai in the Russian Far East, near which the famous borosilicate deposit where this mineral was discovered is located. It was approved by the International Mineralogical Association (IMA) as a new mineral species under number IMA2019-114.

Properties

Mohs hardness
6
Luster
Vitreous
Streak
White
Density
2.83
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Key diagnostic features of dalnegorskite include its mode of occurrence – typically as white, fibrous or bladed aggregates. Its vitreous luster, colorless or white color, and perfect cleavage are also characteristic. It reacts with hydrochloric acid. ## Distinguishing from Similar Minerals Dalnegorskite can be confused with other white, fibrous silicates, such as wollastonite or some zeolites. It differs from wollastonite by its chemical composition (presence of manganese) and slightly different optical properties. Accurate identification requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms It forms elongated, bladed, or acicular crystals that combine into radial, fibrous, or tangled aggregates. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Dalnegorskite forms in contact zones between volcanic rocks (andesites) and carbonate rocks (limestones). It is a product of metasomatic processes occurring in skarns. It occurs in calcite veins cutting through these formations. ## Mineral Associations This mineral co-occurs with calcite, datolite, quartz, and other calcium silicates. ## Localities The only confirmed locality of dalnegorskite in the world is its type locality – the boron deposit in Dalnegorsk, Primorsky Krai, Russia. This is the only site from which specimens of this mineral are obtained.

Rarity

Very rare

For collectors

## Quality Criteria As a monogenetic mineral (known only from one locality) and very rare, every specimen is valuable to collectors specializing in systematics or minerals from Russia. The most desirable specimens are those with clearly formed, rich aggregates of fibrous or bladed crystals, preferably contrasting with a calcite matrix. The size and purity of the aggregates significantly increase the value of the specimen. ## Popular Localities The only source of dalnegorskite specimens is the borosilicate deposit in Dalnegorsk, Russia. Specimens from this location are the only ones available on the collector's market.

Care and storage

## Cleaning Due to the fibrous and delicate nature of the aggregates, caution is advised. It is best to use compressed air to remove dust. If necessary, a soft brush and distilled water can be used, avoiding strong friction. ## What to Avoid Contact with acids and strong chemicals, which can damage the mineral, should be avoided. Due to its perfect cleavage, specimens are sensitive to impacts and mechanical pressure. There are no specific recommendations regarding exposure to light or temperature, but extreme conditions should generally be avoided. ## Storage Dalnegorskite specimens should be stored in separate, padded boxes to protect them from mechanical damage and contact with harder minerals. Delicate, fibrous aggregates are particularly susceptible to crumbling.

Sources

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