Marinaite

Chemical formula: Cu²⁺₂Fe³⁺O₂(BO₃)

Marinaite is a rare copper and iron borate, forming black, prismatic crystals with a strong metallic luster.

## Characteristics Marinaite is a mineral from the ludwigite group, a copper and iron oxyborate. It occurs as elongated, prismatic crystals, which can reach up to 0.3 mm in length and 0.05 mm in width. It also forms granular aggregates and radial clusters. Its color is usually black, sometimes with a brownish tint, and on thin edges, it can be translucent brownish-yellow. ## Physical Properties This mineral is characterized by a strong, metallic luster. It is opaque, becoming translucent only in very thin fragments. Its density, calculated based on the formula and cell parameters, is 5.026 g/cm³. The hardness has not been precisely measured but is estimated to be around 5 on the Mohs scale, similar to other minerals in its group. ## Colors and Varieties Marinaite is black to brownish-black. No color or commercial varieties have been distinguished. ## History and Name The mineral is named in honor of Marina Anatolyevna Zadov (born 1961), a Russian mineral collector from Moscow, who significantly contributed to the study of volcanic fumarole mineralogy. Marinaite was approved as a new mineral species by the International Mineralogical Association (IMA) in 2019 (IMA2019-054). It was discovered at the Tolbachik volcano in Kamchatka. ## Uses Due to its extreme rarity and microscopic crystal sizes, marinaite has no industrial applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Mohs hardness
5
Luster
Metallic
Streak
yellow to light-brown
Density
5.026
Fracture
Splintery
Transparency
Translucent,Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of marinaite requires advanced analytical techniques. Under collecting conditions, identification is based on appearance (black, prismatic crystals with a metallic luster), locality (fumaroles of Tolbachik volcano), and associated minerals. A streak of yellow to light brown is a characteristic feature. Final confirmation requires chemical analysis (EDS) and X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Marinaite is visually very similar to other black, acicular minerals from the ludwigite group and related borates, such as ludwigite, vonsenite, as well as copper and iron oxides (e.g., tenorite). Certain distinction from these minerals is possible only through laboratory methods, as all form similar black, prismatic crystals in the same environment. ## Crystal Forms Marinaite forms elongated, prismatic crystals with a rhombic cross-section. They occur as single, well-formed needles or in radial and tangled aggregates.

Geological environment

## Genesis Marinaite is a mineral of volcanic origin. It forms through sublimation from hot gases (exhalations) in basaltic volcanic fumaroles. It crystallizes at high temperatures, above 600°C, in an oxidizing environment, directly from the gas phase on the surface of volcanic rocks. ## Mineral Associations This mineral occurs in association with other rare volcanic fumarole minerals. At its type locality (Tolbachik volcano), it was found in association with hematite, tenorite, ludwigite, saffranite, fluoborite, sylvite, and halite. ## Localities The only confirmed locality of marinaite in the world is its type locality – fumaroles formed during the 2012-2013 fissure eruption of Plosky Tolbachik volcano. It is located in the Tolbachik volcanic field in Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, marinaite is primarily evaluated based on the quality and richness of the specimen. The most desirable samples are those with numerous, well-formed, sharply terminated crystals forming visually attractive aggregates. Contrast with lighter matrix rock and the presence of rare associated minerals also increase the collectible value of the specimen. The size of individual crystals, although microscopic, is an important factor – the larger, the more valuable. ## Popular Localities The only source of marinaite specimens is its type locality at the Tolbachik volcano in Kamchatka. Specimens from this location are highly valued by collectors specializing in volcanic minerals and micromounts.

Care and storage

## Cleaning Marinaite specimens are extremely small and delicate. Mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove dust. Do not use water or any chemicals. ## What to Avoid As a product of volcanic exhalations, this mineral may be unstable under surface conditions. Avoid contact with water, acids, bases, and abrupt changes in temperature and humidity. It should not be exposed to direct sunlight. ## Storage Specimens should be stored under stable conditions, preferably in closed, airtight "micromount" containers that protect against dust, moisture, and mechanical damage. Store in a dry place with a constant temperature.

External references

Sources

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