Cetineite

Chemical formula: NaK₅Sb³⁺₁₄S²⁻₆O₁₈·6H₂O

Cetineite is a rare sulfosalt mineral, forming characteristic, acicular crystals of an intense red color.

## Characteristics Cetineite is a complex sulfosalt mineral of antimony, sodium, and potassium. It occurs as slender, acicular or fibrous crystals, often forming radial or tangled aggregates, as well as crusts. Its most characteristic feature is an intense, deep red color, somewhat resembling realgar, with which it is sometimes confused. ## Physical Properties Cetineite crystals are very brittle and delicate. This mineral is characterized by a silky or slightly vitreous luster. It is opaque, and its Mohs hardness is approximately 3.5. The density ranges from 4.13 to 4.25 g/cm³. ## Colors and Varieties Cetineite occurs in a characteristic, deep red color. No color or commercial varieties are distinguished. ## History and Name The mineral's name comes from its discovery locality – the Le Cetine di Cotorniano mine in Tuscany, Italy. It was first described in 1987 by Paolo Orlandi, Stefano Merlino, Marco Pasero, and Giovanni Vezzalini and approved by the International Mineralogical Association (IMA) in the same year. ## Uses Due to its rarity, small crystal size, and fragility, cetineite has no industrial applications. It is solely a mineral of scientific and collectible importance, sought after by specialized collectors.

Properties

Mohs hardness
3.5
Color
Orange-red
Luster
Silky
Streak
Orange
Density
0
Cleavage
on {1000}
Fracture
Uneven
Transparency
Transparent,Translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Cetineite can be identified by its characteristic, intense red color and acicular or fibrous crystal habit, often forming radial aggregates. It occurs in a specific geological environment, in association with other antimony minerals. ## Distinguishing from Similar Minerals Cetineite is sometimes confused with realgar, which also has a red color but typically forms larger, prismatic crystals and has a different genesis. Kermesite is also red and acicular, but it forms as a result of stibnite oxidation. Distinguishing it from other rare, red antimony minerals often requires advanced chemical (EDS) or X-ray (XRD) analyses. ## Crystal Forms Crystals are hexagonal, very thin, and elongated in the form of needles or hairs. They usually occur as radial or tangled aggregates, as well as felt-like crusts on the host rock.

Geological environment

## Genesis Cetineite is a secondary mineral, forming in the oxidation zones of antimony deposits. It forms at low temperatures through hydrothermal processes that alter earlier antimony minerals, such as stibnite, in an alkali-rich (sodium and potassium) environment. ## Mineral Associations This mineral co-occurs with other secondary antimony minerals, such as senarmontite, valentinite, kermesite, mopungite, as well as with stibnite, native sulfur, calcite, and quartz. ## Localities The most important and type locality is the antimony mines in the Le Cetine di Cotorniano area in Tuscany, Italy. It is also known from several other localities worldwide, including the Casali mine near Su Suergiu in Sardinia (Italy) and Turecká in the Banská Bystrica region in Slovakia.

Rarity

Rare

For collectors

## Quality Criteria The most prized cetineite specimens are those that possess rich, dense clusters of intensely red, acicular crystals, forming contrasting crusts on light host rock. The extent of surface coverage and the absence of damage to the delicate needles are important. Specimens with well-defined, radial aggregates are particularly sought after. ## Popular Localities By far the most classic and valued specimens come from the type locality – Le Cetine di Cotorniano in Tuscany, Italy. Material from this location is considered exemplary for the species.

Care and storage

## Cleaning Cetineite specimens are extremely delicate and brittle. Mechanical cleaning, including the use of brushes, should be avoided. If absolutely necessary, compressed air can be carefully used from a safe distance to remove dust. However, it is generally recommended to leave specimens undisturbed. ## What to Avoid Contact with water and all chemicals should be avoided. The mineral is sensitive to changes in temperature and humidity. Prolonged exposure to strong light can cause fading of the intense red color, so it should be protected from direct sunlight. ## Storage It is recommended to store specimens in closed, stable containers (such as "micromount boxes") to protect them from mechanical damage, dust, and humidity changes. They should ideally be kept in a dark and dry place.

External references

Sources

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