Medaite

Chemical formula: Mn₂+₆V₅+Si₅O₁₈(OH)

Medaite is a rare manganese and vanadium silicate, forming small, orange-red crystals with a vitreous luster.

## Characteristics Medaite is a very rare mineral from the silicate group, chemically classified as a manganese and vanadium silicate. It occurs as very small, prismatic or tabular crystals, rarely exceeding 1 mm in length. It typically forms aggregates or is disseminated in the host rock. Its characteristic feature is an intense, orange-red to reddish-brown color. ## Physical Properties Medaite crystals exhibit a vitreous luster. This mineral is relatively hard, with a Mohs hardness of approximately 5. It is transparent to translucent. Due to the small size of the crystals, many of its physical properties are difficult to observe without specialized equipment. ## Colors and Varieties This mineral is monochromatic, meaning it occurs in only one color range. Its color varies from orange-red to reddish-brown. No color or commercial varieties have been identified. ## History and Name The mineral's name comes from Francesco Meda (1934-1984), an Italian mineral and micromount collector who first discovered this mineral. Medaite was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 1988. The type locality from which it originates is the Molinello mine in the Graveglia Valley, Liguria, Italy. ## Uses Medaite has no industrial applications. Its significance is purely scientific and collectible, being a coveted item among collectors specializing in rare minerals and micromounts.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: Pale orange
Density: 3.74
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Field identification of medaite is practically impossible. In a collection, it is recognized by its characteristic orange-red color, vitreous luster, and prismatic shape of very small crystals. Association with the locality is crucial – it occurs in manganese deposits. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD) or Raman spectroscopy. ## Distinguishing from Similar Minerals It can be confused with other rare, red minerals from manganese deposits, such as piemontite or some garnets (spessartine). Distinguishing it from these minerals based on visual characteristics is extremely difficult and often impossible without chemical analysis. However, medaite is usually much smaller and forms more elongated, prismatic crystals than spessartine. ## Crystal Forms Medaite crystals are prismatic, often elongated and flattened, with a cross-section resembling a rectangle. They usually occur as single, isolated crystals or small, radial aggregates on the host rock.

Geological environment

## Genesis It is a mineral of metamorphic origin. It forms as a result of low-grade metamorphism of manganese-rich siliceous sediments (radiolarites) under zeolite to prehnite-pumpellyite facies conditions. It is a product of reactions occurring under specific pressure and temperature conditions, with the presence of vanadium. ## Mineral Associations This mineral occurs in association with other manganese minerals. It most commonly co-occurs with quartz, braunite, ganophyllite, piemontite, rhodonite, cryptomelane, and hematite. ## Localities The only confirmed and well-documented occurrences of medaite in the world are in Italy, in the Liguria region. These are the manganese mines in the Graveglia Valley, such as Molinello (type locality), Valgraveglia, and Cassagna.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a medaite specimen is primarily assessed based on the size and habit of the crystals. Most valued are specimens with clearly visible, well-formed, transparent crystals of intense, orange-red color. The contrast with the rock matrix and the presence of associated minerals, which confirm its natural origin, are also important. ## Popular Localities The highest quality specimens, which serve as a standard for this mineral, come from its type locality – the Molinello mine in Liguria, Italy. Specimens from other mines in the Graveglia Valley are also valued, but Molinello is the most renowned source of collectible medaite.

Care and storage

## Cleaning Medaite specimens, due to their extreme rarity and small size, should be cleaned with the utmost care. Only gentle dust removal using an air blower (photographic bulb) is recommended. Any contact with water or chemicals should be avoided. ## What to Avoid Avoid ultrasonic cleaners, all chemical solvents, acids, and bases. The crystals are fragile and sensitive to mechanical shocks. Do not expose specimens to sudden temperature changes. ## Storage The best way to store medaite is to place it in a specialized micromount box, which protects it from dust, mechanical damage, and direct contact. Store in stable conditions, away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)