Hakite-(Hg)

Chemical formula: Cu₁+₆(Cu₁+₄Hg₂+₂)Sb₃+₄Se₂-₁₃

A rare copper, mercury, and antimony selenide with a metallic luster, belonging to the tetrahedrite group.

## Characteristics Hakite-(Hg) is a rare mineral from the tetrahedrite group, a complex selenide of copper, mercury, and antimony. It typically occurs as small, embedded grains, rarely forming tiny tetrahedral crystals. Its surface has a characteristic metallic luster. It is an opaque mineral. ## Physical properties This mineral has a hardness of approximately 4.5 on the Mohs scale. The luster is strongly metallic. Due to its occurrence as small grains, other physical properties, such as density, are difficult to measure precisely. ## Colors and varieties The observed colors of hakite-(Hg) range from grayish-brown to creamy-white. No named varieties are distinguished. ## History and name The name "hakite" honors the Czech mineralogist and geochemist Jaroslav Hak (1931-1997). The suffix "-(Hg)" indicates the dominance of mercury (Latin: *hydrargyrum*) in a specific position within the mineral's crystal structure. It was first described in 1970. ## Applications Due to its extreme rarity, hakite-(Hg) has no industrial applications. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 4.5
Luster: Metallic
Streak: White
Density: 0
Transparency: Opaque
Crystal system: Isometric

Diagnostic features

## Identification Identification of hakite-(Hg) is extremely difficult without advanced analytical methods. Preliminary identification is based on its metallic luster, color (grayish-brown to creamy-white), and co-occurrence with other selenides in a specific geological environment. A white streak is a helpful but not unique feature. Definitive identification requires chemical analysis (e.g., EDS) to confirm the presence of copper, mercury, antimony, and selenium. ## Distinguishing from similar minerals It can be confused with other selenides from the tetrahedrite group, such as giraudite, hakite-(Zn), or tetrahedrite-(Hg), as well as with other sulfides and selenide minerals with a metallic luster. Visual distinction is practically impossible and requires specialized research equipment. ## Crystal forms It crystallizes in the isometric system, theoretically forming tetrahedral crystals. In practice, however, it is most often found as anhedral (irregular) grains, less than a millimeter in size, embedded in other minerals.

Geological environment

## Genesis This is a hydrothermal mineral, forming in calcite-selenide veins cutting volcanic rocks (andesites) or in polymetallic deposits. It forms under low to medium temperature conditions from solutions rich in selenium, copper, mercury, and antimony. ## Mineral associations It most commonly co-occurs with other selenides, such as berzelianite, umangite, bukovite, eskebornite, clausthalite, as well as with calcite, uraninite, hematite, and pyrite. ## Localities The most important and type locality is the Předbořice deposit in the Czech Republic. It has also been reported from the Tumiñico mine in Sierra de Cacho, Argentina, and the Baccu Locci mine in Sardinia, Italy. All these localities are known for their unique selenide mineralogy.

Rarity

Very rare

For collectors

## Quality criteria The collecting appeal of hakite-(Hg) is determined primarily by its extreme rarity and scientific value. Since this mineral forms only microscopic grains, specimens with visible, even small, aggregates of confirmed identity are highly prized. The best specimens are those with rich associations of other rare selenides from the type locality in the Czech Republic. ## Popular localities Specimens from the Předbořice deposit in the Czech Republic, which is its type locality, are by far the most valued and sought after by specialist collectors.

Care and storage

## Cleaning Hakite-(Hg) specimens are usually very small and embedded in the rock matrix. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used to remove dust. Avoid contact with water and any chemical agents. ## What to avoid As a selenide containing mercury, this mineral is potentially sensitive to chemicals, especially acids. Avoid sudden temperature changes, ultrasonics, and exposure to moisture. Due to its mercury content, caution should be exercised, and dust inhalation should be avoided. ## Storage It is recommended to store specimens in stable conditions, in closed, dry containers or display cases, away from direct sunlight and heat sources. The label should include a warning about mercury content.

External references

https://www.mindat.org/min-1803.html