Melanovanadite

Chemical formula: CaV⁴⁺₂V⁵⁺₂O₁₀·5H₂O

Melanovanadite is a rare, hydrated calcium vanadium oxide, forming almost black, prismatic crystals with a vitreous luster.

## Characteristics Melanovanadite is a rare mineral from the oxide group, chemically classified as a hydrated calcium vanadium oxide. Its name, derived from the Greek words *melanos* (black) and *vanadium*, accurately describes its typical appearance. It usually forms small, prismatic or tabular crystals, often gathered in radial or fan-shaped aggregates. Specimens have a characteristic, very dark, almost black color with a greenish or brownish tint. ## Physical Properties Melanovanadite crystals exhibit a vitreous, sometimes slightly metallic luster. This mineral is relatively soft; its Mohs hardness is about 2.5, which means it can be scratched with a fingernail. It is a rather brittle mineral. Its density is higher than average, approximately 3.48 g/cm³. Crystals are usually translucent on thin edges, and opaque in thicker parts. ## Colors and Varieties The dominant and essentially sole color of melanovanadite is black, often with a deep green or brown tint, especially visible in strong light. No color or commercial varieties are distinguished. ## History and Name The mineral was first described in 1921 by Waldemar T. Schaller based on material from the Minas Ragra mine in Peru. The name refers to its black color (Gr. *melanos*) and chemical composition with dominant vanadium. ## Applications Melanovanadite has no industrial application. Its significance is purely scientific and collectible, as a rare and well-defined representative of vanadium minerals.

Properties

Mohs hardness
2.5
Color
Black; dark reddish brown in transmitted light
Luster
Vitreous
Streak
Dark reddish brown
Density
2.55
Cleavage
On {010}, perfect.
Fracture
Uneven
Transparency
Opaque
Crystal system
Triclinic

Diagnostic features

## Identification Melanovanadite can be identified by its black color with a greenish or brownish tint, vitreous luster, and characteristic radial aggregates of small, prismatic crystals. Its low hardness (approx. 2.5) and greenish-brown streak are also important diagnostic features. ## Distinguishing from Similar Minerals This mineral is sometimes confused with other black vanadium minerals, such as hewettite or pascoite, which, however, often have different crystal forms and properties (e.g., pascoite is orange-red). From more common black minerals, such as schorl tourmaline or hornblende, it is distinguished by its significantly lower hardness, specific streak, and occurrence environment in the oxidation zones of vanadium deposits. ## Crystal Forms Melanovanadite crystallizes in the triclinic system. It most often forms elongated, prismatic or flattened, tabular crystals. These crystals rarely occur individually, usually forming fan-shaped, radial, or stellate aggregates, as well as fibrous masses and crusts.

Geological environment

## Genesis Melanovanadite is a secondary mineral, forming in the oxidation zones of vanadium deposits. It forms as a result of weathering and alteration of primary vanadium minerals, often in sedimentary rocks, such as sandstones or shales, which contain dispersed organic matter. ## Mineral Associations This mineral often co-occurs with other secondary vanadium minerals. Its most common associations include pascoite, hewettite, fernandinite, as well as uranium minerals like carnotite and tyuyamunite. Gypsum and calcite may also accompany it. ## Localities The most important and historical locality for melanovanadite is its type locality - the Minas Ragra mine in the Pasco region of Peru. Significant specimens also come from the Paradox Valley area in Montrose County, Colorado (USA), and from other vanadium deposits in the Colorado Plateau region (Utah, Colorado, Arizona states).

Rarity

Rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, sharp crystals forming aesthetic, radial or fan-shaped aggregates. Intense, deep black color with a distinct luster is highly prized. Contrast with light matrix rock (e.g., sandstone) also enhances the visual appeal of the specimen. Crystal size is important, as they are usually small. ## Popular Localities Undoubtedly, the most classic and sought-after specimens come from the historical locality of Minas Ragra in Peru. Material from various mines in the Colorado Plateau region of the USA, which have provided many good quality specimens, is also often found on the collector's market.

Care and storage

## Cleaning Melanovanadite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its low hardness and potential reactivity, avoid washing in water, and especially using any detergents. If it is necessary to remove loose contaminants, compressed air can be used from a safe distance. ## What to Avoid Contact with acids and other chemicals that could damage or dissolve the mineral must be strictly avoided. Melanovanadite is brittle, so it must be protected from impacts and falls. It should not be heated or exposed to prolonged moisture. ## Storage Collectible melanovanadite specimens are best stored in closed, padded boxes or display cases to protect them from dust and mechanical damage. It should be isolated from other, harder minerals that could scratch it.

External references

Sources

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