Hanswilkeite

Chemical formula: KFe³⁺S²⁻₂

Hanswilkeit is a rare potassium iron sulfide, distinguished by its deep purple color and occurrence in pyrometamorphic rocks.

## Characteristics Hanswilkeit is a sulfide mineral, chemically classified as a potassium iron sulfide. It forms very small, platy crystals with a hexagonal outline, reaching sizes up to 100 micrometers. Its most characteristic visual feature is an intense, deep purple color. It typically occurs as fine aggregates within the host rocks. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2. Its density, calculated from crystallographic data, is 2.65 g/cm³. It exhibits a metallic luster. It is opaque. ## Colors and Varieties The dominant and only described color of hanswilkeit is deep purple. No color or commercial varieties have been distinguished. ## History and Name The mineral's name honors the German mineralogist, Professor Hans-Jürgen Wilke (1926–2014), in recognition of his contributions to the study of mineral deposits and parageneses. Hanswilkeit was approved as a new mineral species by the International Mineralogical Association (IMA) in 2015. Its discovery was made in the Hatrurim Formation in Israel. ## Uses Hanswilkeit has no industrial applications. Its significance is purely scientific and collector-oriented, as a rare and unusual sulfide.

Properties

Mohs hardness: 2-0
Luster: Metallic
Streak: brown-black
Density: 2.654
Cleavage: Moderate cleavage was observed along the c-axis
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Amateur identification of hanswilkeit is practically impossible due to the microscopic size of its crystals. Its characteristic features include a deep purple color, metallic luster, and occurrence in the specific pyrometamorphic environment of the Hatrurim Formation. Definitive identification requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS) and X-ray diffraction. ## Distinguishing from Similar Minerals Due to its unique color and paragenesis, it is difficult to confuse it with other minerals in its typical locality. Theoretically, other rare sulfides may exhibit similar luster but differ in color and chemical composition. ## Crystal Forms Hanswilkeit forms very small, platy crystals with a pseudohexagonal habit, rarely exceeding 100 micrometers. They occur as single flakes or small aggregates embedded in the rock.

Geological environment

## Genesis Hanswilkeit is a mineral of pyrometamorphic origin. It forms as a result of natural combustion and melting of sedimentary rocks (marls) at high temperatures and low-pressure conditions. This process leads to the formation of a unique mineral assemblage in rocks referred to as the Hatrurim Formation. ## Mineral Associations This mineral co-occurs with other rare species formed under similar conditions, such as gurimite, barryite, zadokite, aradite, as well as more common minerals like calcite, gypsum, magnetite, and hematite. ## Localities The only confirmed occurrence of hanswilkeit in the world is its type locality in Israel, in the Naẖal Gorer area, within the pyrometamorphic Hatrurim Formation in the Negev Desert.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" type mineral, the value of a specimen is primarily determined by the presence of well-formed, albeit microscopic, crystals of intense purple color. The most desirable specimens are those where hanswilkeit is clearly visible against a contrasting rock matrix and occurs in association with other rare minerals from this locality. Due to their size, the quality of the accompanying photomicrograph is crucial. ## Popular Localities The only source of hanswilkeit specimens is its type locality in the Hatrurim Formation in Israel. Material from this location is extremely limited and rarely appears on the collector's market.

Care and storage

## Cleaning Due to its extreme rarity and small crystal sizes, specimens with hanswilkeit typically do not require and should not undergo mechanical cleaning. Any contaminants should be removed with the utmost care, preferably using compressed air. ## What to Avoid Avoid contact with water, acids, and other chemicals that may react with sulfides. The mineral is soft and brittle, so it must be protected from impacts, scratching, and vibrations. It should not be heated or exposed to temperature changes. ## Storage Specimens with hanswilkeit should be stored in stable conditions, in closed, padded "micromount" boxes to protect them from mechanical damage and dust. Storage in a dry environment, away from direct sunlight, is recommended.

External references

https://www.mindat.org/min-470392.html