Zinc

Chemical formula: Zn

Native zinc is a very rare mineral from the native elements group, being a naturally occurring, crystalline form of metallic zinc.

## Characteristics Native zinc is a natural, metallic form of the element zinc. It occurs extremely rarely, most often as small, irregular grains, plates, or flakes embedded in the host rock. Well-formed crystals are extremely rare and usually take the form of hexagonal tablets or prisms. Fresh surfaces of the mineral have a tin-white or steel-gray color and a strong, metallic luster. When exposed to air, they quickly tarnish and become covered with a gray or bluish oxide film, losing their brilliance. ## Physical Properties Zinc is a very soft mineral, with a Mohs hardness of only 2, meaning it can be scratched with a fingernail. It is relatively heavy, with a density of about 7.14 g/cm³. As a metal, it is malleable and ductile, meaning it can be hammered and drawn into wires. It exhibits excellent cleavage in one plane, parallel to the crystal base. ## Colors and Varieties This mineral does not form colored varieties. Its color is constant - tin-white to steel-gray. Differences in the appearance of specimens result mainly from the degree of surface oxidation (patina). ## History and Name The name zinc comes from the German word "Zink," whose etymology is unclear, but as a metal, it was known in Europe since the 16th century. As a mineral, native zinc was first scientifically described and recognized as a distinct species much later, and its type locality is in the Nareeb Nareeb formation in Australia. ## Applications Due to its extreme rarity, native zinc has no industrial applications. It is solely an object of interest for collectors and scientists studying mineral-forming processes under reducing conditions.

Properties

Mohs hardness: 2
Luster: Metallic
Streak: Bluish-gray
Density: 7.14
Cleavage: Perfect on {0001}
Fracture: Hackly
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Native zinc can be identified by its metallic luster, tin-white color on a fresh fracture, very low hardness (2 on the Mohs scale), and relatively high density. Its malleability is also characteristic – it does not crumble when struck but flattens. The streak, or the color of the powdered mineral, is bluish-gray. ## Distinguishing from Similar Minerals Native zinc can be confused with other native elements: - **Native lead** is even softer (hardness 1.5), heavier (density >11 g/cm³), and leaves a dark gray, smudgy streak. - **Native silver** is slightly harder (2.5-3), heavier (density ~10.5 g/cm³), and has a white streak. - **Native platinum** is much harder (4-4.5) and much heavier (density >15 g/cm³). It should be noted that many "native zinc" specimens on the market are actually metallurgical products (anthropogenic), which often take the form of fanciful aggregates.

Geological environment

## Genesis Native zinc forms under strongly reducing (anoxic) geological conditions. Its formation is a very rare phenomenon. It can crystallize from hot, metal-rich hydrothermal solutions with low sulfur content. It is found in some volcanic rocks, in alteration zones of ore deposits (e.g., in the famous Franklin deposit in the USA), and also as a sublimation product in active volcanoes or burning coal dumps. ## Mineral Associations Depending on the location, native zinc coexists with various minerals. In the Franklin deposit (New Jersey, USA), it is associated with franklinite, willemite, and zincite. In other places, it is found in association with native copper, native silver, native lead, and various sulfides. ## Localities The most important confirmed localities for natural native zinc include: - Nareeb Nareeb, Victoria, Australia (type locality). - Mines in the Franklin and Sterling Hill area, New Jersey, USA. - Kasergy, Chelyabinsk Oblast, Russia. - Dugway Proving Ground, Utah, USA. - Olkusz region in Poland (historical occurrences). - Some volcanoes, e.g., Tolbachik in Kamchatka.

Rarity

Very rare

For collectors

## Quality Criteria The most important criterion for evaluating a native zinc specimen is the absolute certainty of its natural origin, confirmed by reliable documentation. Anthropogenic specimens (originating from metallurgical processes) are practically worthless to mineral collectors. For natural specimens, those with well-formed, visible crystals are most highly valued. The size of the crystals or aggregates and aesthetic associations with other rare minerals, e.g., from Franklin, are also important. ## Popular Localities The most well-known and valued natural native zinc specimens by collectors come from historical finds in the Franklin and Sterling Hill mines in the USA and from some localities in Russia. Specimens from these places, especially those with visible crystals, fetch very high prices on the collector's market.

Care and storage

## Cleaning Native zinc specimens should be cleaned with the utmost care due to their softness. The safest method is to use a soft brush to remove dust. If washing is necessary, use distilled water and immediately dry the specimen thoroughly to prevent oxidation. Ultrasonic cleaners must not be used. ## What to Avoid Zinc is chemically reactive. Contact with acids and bases, which dissolve it, must be strictly avoided. Humid air causes it to tarnish and form films, so it should be protected from moisture. As a very soft mineral, it is susceptible to scratches – it should not come into contact with harder minerals. ## Storage It is recommended to store native zinc specimens in a dry environment, preferably in closed, airtight containers (e.g., membrane boxes) or in display cases with a desiccant. To avoid mechanical damage, each specimen should be stored separately.