Parageorgbokiite

Chemical formula: Cu₂+₅O₂(Se₄+O₃)₂Cl₂

Parageorgbokiite is a rare copper selenite, distinguished by its intense green color and occurrence as small, tabular crystals.

## Characteristics Parageorgbokiite is a mineral from the selenite group, chemically a hydrated copper selenite with chlorine. It forms very small, tabular or bladed crystals, which rarely exceed 0.3 mm. They usually occur in the form of radial or chaotic aggregates, as well as thin coatings and granular masses on volcanic rocks. Its most characteristic feature is its vivid, emerald-green color. ## Physical Properties Parageorgbokiite crystals exhibit a vitreous luster. The mineral is transparent to translucent. Due to the small size of the crystals, precise determination of hardness and density is difficult, but it is estimated based on chemical composition and comparisons with similar minerals. ## Colors and Varieties This mineral occurs in one characteristic color – emerald-green or simply green. No color or commercial varieties are distinguished. ## History and Name Parageorgbokiite was first described in 2002 by a team of mineralogists: L.P. Vergasova, S.K. Filatov, T.F. Semenova, V.V. Ananiev, and P.M. Burns. Its name refers to its structural similarity to georgbokiite. Both minerals were named in honor of Georgiy Borisovich Bokiy (1909–2001), a distinguished Russian crystallographer from Moscow State University. ## Uses Parageorgbokiite has no industrial application. Its significance is purely scientific and collectible, as a rare and interesting representative of selenites from a unique locality.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: Green
Density: 4.23
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Parageorgbokiite is identified by its characteristic emerald-green color, its occurrence as small, tabular crystals forming aggregates, and its unique geological environment – volcanic exhalations. It reacts vigorously with hydrochloric acid. ## Distinguishing from Similar Minerals It can be confused with other secondary copper minerals of green color, such as georgbokiite, sofiite, or chloromenite, which occur in the same environment. Certain distinction from georgbokiite requires advanced analytical methods (e.g., structural X-ray diffraction), as they are visually almost identical. It differs from them by subtle optical properties and crystallographic parameters. ## Crystal Forms Crystals are very small, usually tabular or bladed, flattened parallel to {010}. They form radial or irregular aggregates, as well as thin crusts and coatings on the surface of basaltic lava.

Geological environment

## Genesis Parageorgbokiite is a fumarolic mineral. It forms as a result of the resublimation of volcanic gases at temperatures of 150-200°C. It crystallizes directly on porous basaltic lava near active fumaroles. ## Mineral Associations This mineral co-occurs with other rare selenites and sulfates formed under similar conditions. It is most often accompanied by: georgbokiite, sofiite, chloromenite, cotunnite, halite, sylvite, tenorite, and hematite. ## Localities The only confirmed locality of parageorgbokiite in the world is its type locality – the fumarole field on the northern cone of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The most prized parageorgbokiite specimens are those with rich, well-formed crystal aggregates on a small fragment of matrix rock. The intensity and purity of the emerald-green color is a key factor. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. Contrast with a light matrix rock enhances visual appeal. ## Popular Localities The only source of parageorgbokiite specimens is the Tolbachik volcano in Kamchatka. Material from this locality is extremely rare on the collector's market and sought after by specialists in systematic minerals and rare species.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Contact with water is absolutely inadvisable, as the mineral is soluble in it. All wet cleaning methods and ultrasonics should be avoided. ## What to Avoid Avoid contact with water, acids, chemicals, and high air humidity, which can lead to the slow decomposition of the mineral. Specimens are susceptible to abrasion and mechanical damage due to their low hardness and small crystal size. ## Storage It is recommended to store specimens in airtight, sealed containers (e.g., "membrane box" or "perky box") away from moisture and contaminants. Display should be in stable conditions, without direct sunlight and temperature fluctuations.

Sources

IMA Mineral List (CNMNC)