Milkovoite

Chemical formula: Cu<sup>2+</sup><sub>4</sub>O(PO<sub>4</sub>)(As<sup>5+</sup>O<sub>4</sub>)

Milkovoite is a very rare mineral from the phosphate and arsenate group, forming microscopic, tabular crystals of an intensely green color.

## Characteristics Milkovoite is a hydrated copper phosphate-arsenate, occurring as very small, tabular or bladed crystals, which rarely exceed 0.2 mm in length. It forms thin coatings, rosette-like aggregates, or appears as dispersed clusters on the surface of the host rock. Its characteristic feature is an intense, emerald-green color. ## Physical Properties The crystals exhibit a vitreous luster. Due to the microscopic size of the crystals, most physical properties, such as hardness or density, have not been precisely determined. ## Colors and Varieties This mineral occurs in a uniform, emerald-green color. No color varieties or commercial forms are known. ## History and Name The mineral's name comes from its discovery locality – Tolbachik volcano on the Kamchatka Peninsula in Russia, specifically from the Milkovo lava field. It was officially approved by the International Mineralogical Association (IMA) in 2023 (IMA2023-088). The research team that described the mineral consisted of Russian mineralogists, including Igor V. Pekov. ## Uses Milkovoite has no industrial application. Its significance is purely scientific and collectible, as a unique and newly discovered mineral.

Properties

Luster
Vitreous
Streak
Green
Cleavage
Perfect on {010}
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of milkovoite is based on its characteristic emerald-green color, specific form of microscopic, tabular crystals, and occurrence in volcanic exhalation products. Identification requires advanced analytical techniques, such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from similar minerals Milkovoite can be confused with other secondary green copper minerals, such as euchroite, pseudomalachite, or other rare arsenates and phosphates from volcanic fumaroles (e.g., lammerite, eriocalcite). Differentiation with the naked eye is impossible – key factors are: crystal habit (thin tablets), environment of occurrence (volcanic exhalations), and confirmation of chemical composition (simultaneous presence of phosphorus and arsenic). ## Crystal forms Crystals are very small, thin, and tabular, often with a rectangular or bladed outline. They usually form irregular clusters, thin coatings, or small, rosette-like aggregates on the rock surface.

Geological environment

## Genesis Milkovoite is a mineral of volcanic origin, crystallizing from volcanic gases (exhalations) in fumarolic zones. It forms as a result of the reaction of hot gases rich in copper, arsenic, and phosphorus with surrounding volcanic rocks in an oxidizing environment. ## Mineral associations This mineral co-occurs with other products of volcanic exhalations, such as tenorite, hematite, eriocalcite, lammerite, euchroite, and newly discovered copper arsenates and phosphates characteristic of Tolbachik volcano fumaroles. ## Localities The only confirmed locality for milkovoite in the world is its type locality: the Milkovo lava field, formed during the Great Fissure Eruption of Tolbachik (1975-1976) on Tolbachik volcano, Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality criteria Due to the microscopic nature of the mineral, the most important quality criterion is the richness and aesthetics of the crystal clusters on the rock matrix. Specimens with clearly formed, though still microscopic, crystals forming dense aggregates of an intense, emerald-green color are most valued. Contrast with a light host rock also enhances the specimen's attractiveness. ## Popular localities The only source of specimens is the type locality in Kamchatka, Russia. Material from this location is extremely rare and available almost exclusively through specialized channels.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the extreme delicacy and microscopic size of the crystals, any mechanical contact (brushes, water) is highly risky and can lead to the destruction of the mineral. ## What to avoid Avoid contact with water, chemical agents, and ultrasound. The crystals are very brittle and sensitive to shocks and temperature changes. Specimens should not be exposed to direct sunlight. ## Storage It is recommended to store specimens exclusively in specialized, sealed "micromount" boxes, which protect against dust, shocks, and humidity. Display should be away from sources of vibration and direct light.

Sources

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