Mannardite

Chemical formula: Ba(Ti₄+₆V₃+₂)O₁₆

Mannardite is a rare mineral from the hollandite supergroup, an oxide of barium, titanium, and vanadium, forming black, prismatic crystals with a metallic luster.

## Characteristics Mannardite is a rare oxide mineral belonging to the hollandite supergroup. It forms elongated, prismatic crystals with a square or octagonal cross-section, terminated by pyramids. It typically occurs as single, well-formed crystals, reaching up to 2 cm in length, or in the form of radial aggregates. Its characteristic features are its black, opaque color and strong, almost metallic luster. ## Physical Properties Mannardite is a relatively hard mineral, with a Mohs hardness of 7. It has a high density, ranging from 4.28 to 4.33 g/cm³. It is characterized by a strong, submetallic to adamantine luster. It is brittle, and its fracture is conchoidal to uneven. It does not exhibit cleavage. ## Colors and Varieties This mineral is uniform in color – it occurs exclusively in black. No colored varieties or trade names are known. ## History and Name Mannardite was discovered in 1963 but was described and approved as a new mineral by the IMA only in 1984. Its name honors George W. Mannard (1930-1982), a Canadian geologist and Vice President of Exploration for Kidd Creek Mines Ltd., who first found this mineral in Roughrider, British Columbia, Canada. ## Uses Due to its rarity, mannardite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists.

Properties

Mohs hardness: 7
Luster: Submetallic to adamantine
Streak: Gray
Density: 4.28 - 4.33
Cleavage: None
Fracture: Conchoidal to uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Mannardite can be identified by its characteristic habit – long, prismatic crystals with a square cross-section, black color, and strong, submetallic luster. High hardness (7) and density are also helpful in identification. ## Distinguishing from Similar Minerals Mannardite is sometimes confused with other black, prismatic minerals, such as schorl (black tourmaline) or some pyroxenes. It is distinguished from schorl by its tetragonal crystal system (tourmaline is trigonal and has a typical triangular crystal cross-section) and the absence of striations on the prismatic faces. It differs from pyroxenes by its higher hardness and luster. ## Crystal Forms Mannardite crystals are tetragonal, with a prismatic habit, often elongated along the crystallographic axis. They usually have a square or octagonal cross-section and are terminated by tetragonal pyramid faces. They occur as single crystals embedded in the host rock or form radial aggregates.

Geological environment

## Genesis Mannardite forms under specific hydrothermal conditions, in quartz-carbonate veins cutting sedimentary rocks, such as dolomitic siltstones. Its crystallization is associated with the presence of barium, titanium, and vanadium in hydrothermal solutions. ## Mineral Associations This mineral co-occurs with quartz, dolomite, baryte, titanite, rutile, anatase, pyrite, as well as with rare vanadium minerals such as montroseite and doloresite. ## Localities The most important and well-known locality for mannardite, which is also its type locality, is the Roughrider deposit in British Columbia, Canada. Specimens have also been found in the Carlin mine in Eureka County, Nevada (USA), and in the Murun complex on the Aldan Plateau in Siberia, Russia, where it co-occurs with charoite.

Rarity

Very rare

For collectors

## Quality Criteria Most valued by collectors are specimens with well-formed, sharp, and lustrous crystals that stand out clearly from the rock matrix. Large, single crystals exceeding 1 cm in length are particularly sought after, as are aesthetic compositions with associated minerals, e.g., with white quartz or dolomite. The absence of mechanical damage is important. ## Popular Localities By far the most desirable specimens come from the type locality – the Roughrider deposit in British Columbia, Canada. These are characterized by the best crystal development and largest sizes. Specimens from Nevada or Russia are much rarer on the collector's market.

Care and storage

## Cleaning Mannardite specimens can be cleaned using a soft brush and distilled water. Ultrasonic cleaners should be avoided, as they could damage the brittle crystals. ## What to Avoid The mineral is chemically stable; however, contact with strong acids should be avoided. It is not sensitive to light or temperature changes under household conditions. ## Storage Mannardite crystals are brittle, so specimens should be stored in separate boxes or display cases, away from harder minerals that could scratch them. It is best to display them in their original rock matrix, which provides additional protection.

Sources

IMA Mineral List (CNMNC)