Khorixasite

Chemical formula: (Bi<sup>3+</sup><sub>0.67</sub>&#9744;<sub>0.33</sub>)Cu<sup>2+</sup>(V<sup>5+</sup>O<sub>4</sub>)(OH)

A bismuth copper vanadate hydroxide, forming microscopic, tabular crystals of an intensely green color.

## Characteristics Khorixasite is a rare secondary mineral from the vanadate group. It forms very small, tabular or platy crystals, which usually do not exceed 0.2 mm. These crystals often group into spherical or hemispherical aggregates. Its color ranges from yellowish-green to olive-green. Due to the small size of the crystals, it is a mineral almost exclusively available in the form of micromounts. ## Physical Properties It is characterized by a luster ranging from adamantine to greasy. It is a translucent mineral. The Mohs hardness and density have not yet been precisely determined, but the presence of bismuth and copper suggests that it is a mineral with a relatively high density. ## Colors and Varieties This mineral occurs in shades of green, from yellowish-green to olive. No color varieties or commercial varieties have been identified. ## History and Name Khorixasite was first described in 2002 by J. Schlüter, K.-H. Klaska, G. Adiwidjaja, and G. Gebhard. Its name comes from the Khorixas District in Namibia, where its only known occurrence (type locality) is located. ## Uses Khorixasite has no industrial application. Its significance is purely scientific and collectible, being an object of interest for specialists in rare minerals.

Properties

Luster
Adamantine
Streak
Light green
Transparency
Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Amateur identification of khorixasite is practically impossible. Key diagnostic features, however requiring laboratory analysis (XRD, EDS), are its chemical composition (presence of Bi, Cu, and V), characteristic crystal structure, and paragenesis. Visually, a yellowish-green color, tabular form of microcrystals, and occurrence in the only known locality can be a clue. ## Distinguishing from Similar Minerals It can be confused with other green secondary copper minerals, such as mottramite, duftite, or pseudomalachite, especially in the form of microscopic aggregates. Definitive differentiation is only possible based on chemical analysis, which will show the presence of bismuth as a key element. ## Crystal Forms It forms thin, tabular or platy crystals with hexagonal or rhombic outlines. These crystals often occur as radial or spherical aggregates.

Geological environment

## Genesis Khorixasite is a secondary mineral, forming in the oxidation zone of polymetallic, hydrothermal ore deposits. Its occurrence is associated with the weathering of primary bismuth, copper, and vanadium minerals within vein rocks (dolerites). ## Mineral Associations This mineral occurs in association with quartz, calcite, schneiderhöhnite, and a yet-undescribed copper-bismuth arsenate. ## Localities The only confirmed occurrence of khorixasite in the world is Mesopotamia Farm 504 in the Khorixas District, Kunene Region, Namibia. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromount mineral, the collector's value of khorixasite depends on several factors. Specimens with well-formed, sharp crystals forming aesthetic aggregates are most highly prized. The abundance of the mineral on the rock matrix and the color contrast with associated minerals are also important. Purity and lack of damage to the delicate crystals are crucial. ## Popular Localities The only source of specimens is the type locality in Namibia, which makes every specimen from this location a valuable acquisition for specialized collectors.

Care and storage

## Cleaning Khorixasite specimens are extremely delicate and small. To remove dust, use only compressed air from a safe distance or a very soft brush (e.g., squirrel hair). Avoid contact with water and any chemical agents. ## What to Avoid This mineral is sensitive to mechanical damage, abrasion, and shocks. Ultrasonic cleaners, acids, and sudden temperature changes should be absolutely avoided. Due to its rarity, any invasive cleaning methods are discouraged. ## Storage The safest way to store it is in a specialized "micromount" box, which protects the specimen from dust, moisture, and mechanical damage. Avoid exposure to direct sunlight.

Sources

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