Hakite-(Cd)

Chemical formula: Cu1+6(Cu1+4Cd2+2)Sb3+4Se2-13

Hakite-(Cd) is an extremely rare, black mineral from the tetrahedrite group, being a copper and cadmium selenoantimonide.

Description

## Characteristics Hakite-(Cd) is a mineral with a metallic luster and black color. It occurs as very small, irregular (anhedral) grains, not exceeding 200 micrometers in size. These grains are usually intergrown with other selenides, forming complex aggregates that can only be observed under high magnification. ## Physical Properties This mineral has a hardness of approximately 4.5 on the Mohs scale. Its density, calculated based on its chemical composition and unit cell parameters, is 5.45 g/cm³. It is completely opaque, and its luster is described as metallic. ## Colors and Varieties To date, hakite-(Cd) has only been found in black. No color varieties or commercial forms are known. ## History and Name The mineral was officially described and approved as a new species in 2021 by a team of mineralogists led by Jiří Sejkora. The name honors the Czech mineralogist Jaroslav Hak (1931–2009), who first described "hakite" (now known as hakite-(Hg)). The suffix -(Cd) in the name indicates the dominance of cadmium in its chemical composition. The type locality (locus typicus) is Předbořice in the Czech Republic. ## Applications Hakite-(Cd) has no industrial applications. Due to its rarity and microscopic size, it is solely an object of scientific interest and a valuable acquisition for specialized mineral collectors (so-called systematic collectors).

Diagnostic features

## Identification Identification of hakite-(Cd) based on visual characteristics is impossible. Definitive identification requires advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) in a scanning electron microscope (SEM) to determine chemical composition, and X-ray diffraction (XRD) to confirm crystal structure. Geological context and co-occurrence with other rare selenides in a known locality are crucial clues. ## Distinguishing from Similar Minerals With the naked eye and under a microscope, it is practically indistinguishable from many other black minerals with a metallic luster, especially from other members of the tetrahedrite group, as well as from associated selenides and sulfides, such as cadmoselite, clausthalite, or tiemannite. ## Crystal Forms This mineral does not form well-developed crystals. It occurs exclusively as anhedral (irregular, lacking faces) grains, often forming complex intergrowths with other minerals.

Geological environment

## Genesis Hakite-(Cd) forms under low-temperature hydrothermal conditions. At the type locality, it was found in calcite-siderite veins cutting Neoproterozoic, silicified black shales and greywackes. ## Mineral Associations This mineral occurs in association with other, often rare, selenides. The most important associated minerals include: cadmoselite, berzelianite, umangite, tiemannite, chameanite, krut'aite, clausthalite, as well as uraninite, goethite, calcite, and siderite. ## Localities The only confirmed occurrence of hakite-(Cd) in the world is its type locality – the vicinity of Předbořice in the Central Bohemian Region of the Czech Republic.

Rarity

Extremely rare

Collector aspects

## Quality Criteria In the case of microminerals such as hakite-(Cd), the main criterion for value is not aesthetics, but the richness of the specimen (quantity and size of mineral grains on the rock matrix) and the certainty of its identification, confirmed by analytical methods. Specimens with clearly visible associated minerals are also highly valued. ## Popular Localities As the mineral is known from only one location in the world, all collectible specimens come from the type locality in Předbořice, Czech Republic.

Care and storage

## Cleaning Due to the microscopic size of specimens and their fragility, mechanical cleaning is highly inadvisable. If necessary, compressed air can be used to remove dust. Contact with water and any chemical agents should be avoided. ## What to Avoid The mineral is sensitive to acids and other chemical reagents. It should be protected from moisture, which can cause its oxidation. As a relatively soft mineral, it is susceptible to scratches and mechanical damage. ## Storage Hakite-(Cd) specimens should be stored under stable conditions in a dry environment. The best solution is to place them in specialized micromount boxes, which protect against dust, moisture, and physical damage.