Nickeltsumcorite

Chemical formula: Pb₂+(Ni₂+,Fe₃+)₂(As₅+O₄)₂(H₂O,OH)₂

An arsenate of lead, nickel, and iron from the tsumcorite group, forming characteristic brown or yellowish-brown crusts and small crystals.

## Characteristics Nickeltusmcorite is a rare secondary mineral from the arsenate class, belonging to the tsumcorite group. It is a hydrated arsenate of lead, nickel, and iron. It most commonly occurs as thin crusts, earthy aggregates, or forms aggregates of very small, radially arranged crystals. Well-formed, single crystals are extremely rare and achieve small sizes. ## Physical Properties This mineral is characterized by a hardness of 4.5 on the Mohs scale. It has a vitreous to subadamantine luster, and can also be dull in earthy aggregates. It is translucent to opaque. Its density is approximately 5.13 g/cm³. ## Colors and Varieties Nickeltusmcorite ranges in color from yellowish-brown, through reddish-brown, to dark brown. No color varieties or commercial varieties are distinguished. ## History and Name The mineral's name, approved by IMA in 1996, refers to its chemical composition (dominance of nickel) and its structural similarity to tsumcorite, another mineral from this group. The type locality is the famous Tsumeb mine in Namibia, from which the best specimens originate. ## Uses Due to its rarity and small accumulations, nickeltusmcorite has no industrial application. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 4.5
Luster: Vitreous
Streak: Light brown
Density: 5.13
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying nickeltusmcorite based on visual characteristics is very difficult. Key indicators are: brown color, mode of occurrence (crusts, radial aggregates), and most importantly, mineral paragenesis and locality. Definitive identification requires advanced chemical (e.g., EDS) and structural (XRD) analyses. ## Distinguishing from similar minerals Nickeltusmcorite is visually indistinguishable from other minerals of the tsumcorite group, such as tsumcorite, gartrellite, or thometzekite, which often co-occur in the same localities and have similar colors and forms. They differ in the proportions of metals (zinc, copper, iron, nickel), which can only be determined analytically. ## Crystal forms It forms very small, tabular or prismatic crystals, usually gathered in druses, crusts, and rosette-like or radial aggregates. It also occurs as earthy aggregates and masses filling small fissures in the host rock.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation zones (iron caps) of polymetallic, hydrothermal ore deposits rich in arsenic, lead, and nickel. ## Mineral associations It most commonly co-occurs with other secondary arsenates from the tsumcorite group, as well as with willemite, smithsonite, quartz, goethite, tennantite, and helmutwinkleryite. ## Localities The most important and historical locality, from which the world's best specimens originate, is the Tsumeb mine in Namibia. This mineral has also been reported in small quantities in several other places around the world, including the Odenwald region in Germany and the Laurion mines in Greece, however, specimens from these localities are mainly of scientific interest.

Rarity

Rare

For collectors

## Quality criteria The most highly prized specimens are those from the Tsumeb mine in Namibia. The collector's value is determined by the richness of the crust on the rock matrix, the intensity of the color, and the presence of even microscopic but well-defined crystals. Associations with other rare minerals from Tsumeb are also highly desirable. ## Popular localities The only locality of significance for collectors is the Tsumeb mine in Namibia. Specimens from other localities are extremely rare on the market and are usually microminerals.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Ultrasonic cleaners must not be used. ## What to avoid The mineral is sensitive to acids and strong chemicals, which can damage it. High temperatures and sudden changes in temperature should be avoided. As an arsenate, caution is required – avoid inhaling dust and wash hands after contact with the specimen. ## Storage It is recommended to store in stable conditions, in a dry place, away from direct sunlight. It is best kept in a closed display box to protect it from mechanical damage and dust.

Sources

IMA Mineral List (CNMNC)