Koritnigite
Chemical formula: Zn<sup>2+</sup>(As<sup>5+</sup>O<sub>3</sub>OH)·H<sub>2</sub>O
Koritnigite is a rare, hydrated zinc arsenate, forming colorless or white, tabular crystals in the oxidation zones of ore deposits.
Description
## Characteristics Koritnigite is a rare secondary mineral from the arsenate group. It occurs as small, well-formed, tabular or platy crystals, often aggregated into radial or fan-shaped clusters. It is usually colorless, white, or grayish, exhibiting a characteristic luster that distinguishes it from some co-occurring minerals. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3. Its crystals are transparent to translucent. It exhibits perfect cleavage in one plane, where the luster is distinctly pearly, while on other surfaces and fractures it is vitreous. The density of koritnigite is approximately 3.96 g/cm³. ## Colors and Varieties Koritnigite is a mineral with a limited color palette. The most common specimens are colorless, white, and shades of gray. No colored varieties or trade names are distinguished for it. ## History and Name The mineral is named in honor of Sigmund Koritnig (1912–1994), a professor of mineralogy at the University of Göttingen in Germany. It was first described in 1979 by Paul Keller, Heinz Hess, and P. J. Dunn based on specimens from the famous Tsumeb mine in Namibia. ## Uses Due to its rarity and small crystal size, koritnigite has no industrial applications. It is solely an object of scientific and collecting interest.
Diagnostic features
## Identification Characteristic features of koritnigite include its tabular crystal habit, perfect cleavage in one direction, and a distinctly pearly luster on cleavage planes. Its paragenesis – occurrence with other secondary zinc and lead arsenates in oxidation zones – is also an important indicator. ## Distinguishing from Similar Minerals Koritnigite can be confused with other colorless or white secondary minerals. It is distinguished from gypsum by its significantly higher density. It can be mistaken for köttigite, which, however, crystallizes in the monoclinic system and often has a pinkish coloration. It is distinguished from prosperite by its lower hardness. Final confirmation of identity requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Koritnigite crystals are tabular, often elongated and flattened parallel to the cleavage plane. They form characteristic radial or fan-shaped aggregates, as well as small, dispersed groups grown on the host rock.
Geological environment
## Genesis Koritnigite is a secondary mineral, formed in the oxidation zones of hydrothermal polymetallic deposits rich in zinc and arsenic. It forms as a result of the weathering of primary sulfides and arsenides, such as sphalerite and tennantite. ## Mineral Associations This mineral often co-occurs with other rare arsenates. Its typical associated minerals include: adamite, zincolivenite, prosperite, gaitite, tsumcorite, stranskiite, as well as sphalerite, tennantite, and galena as primary minerals. ## Localities The most important and historical locality for koritnigite is the Tsumeb mine in Namibia, which has yielded the world's best specimens. Other confirmed localities include the Lavrion district in Greece and the Bou Azzer region in Morocco. However, these occurrences are much rarer and do not provide specimens of the same quality as Tsumeb.
Rarity
Very rare
Collector aspects
## Quality Criteria The most highly prized koritnigite specimens are characterized by sharply terminated, transparent crystals with a distinct luster, aggregated into aesthetic, radial clusters. Crystal size is of great importance – specimens with crystals exceeding several millimeters are considered exceptional. The value is also enhanced by a contrasting rock matrix or association with other colorful minerals, e.g., green adamite. ## Popular Localities Specimens from the type locality – the Tsumeb mine in Namibia – are by far the most sought after by collectors. They are considered the global standard for this mineral. Specimens from other locations, such as Greece or Morocco, are rare on the market and constitute a valuable addition to specialized collections.
Care and storage
## Cleaning Koritnigite is a soft and brittle mineral, thus requiring very careful cleaning. The safest way to remove dust is with a soft brush or a stream of compressed air from a safe distance. Washing with water should be avoided, and if absolutely necessary, only distilled water should be used, and the specimen should be thoroughly dried immediately. ## What to Avoid As an arsenate, koritnigite is toxic. Inhaling dust should be avoided, and hands should be washed after any contact with the mineral. It must not be heated or exposed to acids and other chemicals. Due to its low hardness, it must be protected from scratching by harder minerals. Prolonged exposure to moisture should also be avoided. ## Storage Koritnigite specimens are best stored in separate, sealed membrane boxes or in display cases away from other minerals that could mechanically damage them. It is important that the container is labeled with a toxicity warning (arsenic content).