Kornelite

Chemical formula: Fe³⁺₂(S⁶⁺O₄)₃·7H₂O

Kornelite is a rare, hydrated iron(III) sulfate, forming delicate, acicular crystals with a characteristic pink or violet color.

## Characteristics Kornelite is a hydrated iron(III) sulfate, occurring as delicate, silky aggregates and crusts. It forms small, acicular or hair-like crystals that rarely reach larger sizes. Due to its nature, it is a very brittle mineral and sensitive to changes in environmental humidity. Its characteristic pale pink to violet color makes it recognizable, despite the small size of its crystals. ## Physical Properties Kornelite crystals exhibit a silky luster. This mineral is transparent and has a relatively low density, approximately 2.3 g/cm³. It is soft and brittle, which makes it extremely difficult to prepare and study. ## Colors and Varieties Kornelite occurs in shades from pale pink to violet. Its color is one of the main diagnostic features. No named varieties of this mineral are distinguished. ## History and Name The mineral was first described in 1888. Its name comes from Kornel Glatzel, a Hungarian geologist who first identified this mineral. The type locality, from which the first studied specimens originated, is Smolník in Slovakia. ## Uses Kornelite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientific institutions.

Properties

Luster
Silky
Streak
White
Density
2.306
Cleavage
On {100}
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Kornelite is primarily identified by its characteristic pink or violet color, silky luster, and form of occurrence – most often as delicate, acicular or fibrous aggregates. Its instability in contact with water and in dry air is also an important diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with other secondary sulfates, such as quenstedtite, into which kornelite transforms due to water loss. However, quenstedtite usually has a more reddish-violet hue. From other pink secondary minerals, like erythrite, it is distinguished by its environment of occurrence (oxidation zones of sulfide deposits, not arsenide deposits) and its solubility in water. ## Crystal Forms Kornelite crystals are elongated, acicular or hair-like, often forming radial or tangled aggregates. It also occurs as silky crusts and coatings on the host rock.

Geological environment

## Genesis Kornelite is a secondary mineral, formed as a result of the weathering (oxidation) of iron sulfide deposits, mainly pyrite and marcasite. It forms in dry conditions, in mines or on dumps, as a product of post-magmatic processes. It is an unstable and often ephemeral mineral, appearing and disappearing depending on the season and humidity. ## Mineral Associations It most often co-occurs with other iron sulfates, such as quenstedtite (into which it transforms), romerite, melanterite, voltaite, as well as with pyrite, marcasite, and gypsum. ## Localities The most important and historical locality is the type locality in Smolník, Slovakia. It is also known from the Rammelsberg mine in the Harz Mountains, Germany, from mines in Copiapó, Chile, and from several locations in the United States, including Utah and California.

Rarity

Rare

For collectors

## Quality Criteria The most prized kornelite specimens are those with well-formed, clearly visible acicular crystals of intense pink or violet color. Aesthetic composition with the rock matrix and the absence of damage to the delicate crystals are also important. Due to its rarity, even small but well-defined aggregates are valuable to collectors. ## Popular Localities Specimens from the type locality in Smolník, Slovakia, and from the Rammelsberg mine in Germany are classics and have historical value. High-quality kornelites also come from dry regions of Chile, e.g., from Sierra Gorda.

Care and storage

## Cleaning Kornelite specimens should not be cleaned with water. The mineral is soluble in water, and even in humid air, it can dehydrate, transforming into quenstedtite. To remove dust, compressed air can be used very carefully from a distance, or a soft brush, avoiding any pressure. ## What to Avoid Contact with water, water vapor, and chemicals must be strictly avoided. Kornelite is unstable in conditions of low air humidity (below 30%), so it should be protected from dry environments. It should not be heated or exposed to direct sunlight. ## Storage Kornelite specimens require storage in airtight containers (e.g., "membrane box" type or sealed acrylic boxes) that ensure a stable humidity level. This is crucial for preserving the mineral's integrity. Due to its brittleness, all vibrations and shocks should be avoided.

External references

Sources

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