Paradocrasite

Chemical formula: Sb<sub>2</sub>(Sb,As)<sub>2</sub>

Paradocrasite is an extremely rare, silvery-white antimony arsenide and antimonide, forming unique, bent or twisted crystals.

## Characteristics Paradocrasite is an exceptionally rare mineral from the alloy group (antimonides). Its most distinctive feature is its mode of occurrence – it forms elongated, often strongly bent, and even twisted crystals with a silvery-white color and metallic luster. The surface of specimens is sometimes covered with a dark gray or black layer of oxidation products, masking the mineral's true color. Due to its rarity and unusual morphology, it is an object of interest for specialized collectors. ## Physical Properties This mineral is opaque and exhibits a strong, metallic luster on fresh surfaces. It is relatively soft, with a Mohs hardness of approximately 2. It is also quite dense, which is typical for antimony-bearing minerals. ## History and Name The name "paradocrasite" comes from the Greek words *paradox* (unexpected, strange) and *krasis* (mixture, alloy), referring to its unusual chemical composition and surprising crystal morphology. The mineral was first described in 1971 by B. F. Leonard, G. A. Desborough, and C. B. Barton based on material from the Red Devil mine in Alaska, USA.

Properties

Mohs hardness
2
Luster
Metallic
Streak
Black
Density
6.59
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification The key diagnostic feature of paradocrasite is its unique morphology – strongly curved, elongated crystals of silvery-white color (on a fresh fracture) and metallic luster. A dark tarnish on the surface is also characteristic. ## Distinguishing from Similar Minerals It can be confused with native antimony or stibarsen. It differs from antimony primarily by its characteristic, bent crystal form. Stibarsen can be similar, but paradocrasite has a different chemical composition and structure, requiring advanced research methods (XRD, EDS) for definitive confirmation. ## Crystal Forms It forms elongated, bladed crystals that are almost always strongly curved, twisted, or deformed. It occurs as individual crystals or loose aggregates.

Geological environment

## Genesis Paradocrasite forms under low-temperature hydrothermal conditions. At its type locality (Red Devil mine), it was found in calcite-quartz veins cutting through shales and sandstones. ## Mineral Associations This mineral co-occurs with native antimony, stibarsen, cinnabar, calcite, and quartz. ## Localities Paradocrasite is an extremely rare mineral, known from only a few localities worldwide. The most important and classic locality is the Red Devil mine in the Sleetmute area of Alaska, USA. It has also been reported from the Krásná Hora mine in the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria The most important criterion for evaluating a paradocrasite specimen is the degree of crystal development and deformation – the more bent and unusual, the more valuable the specimen. The size of the crystals and the presence of associated minerals, which confirm its origin, are also important. Due to its rarity, every authentic specimen is valuable. ## Popular Localities The only source of collector-grade specimens is the historical type locality – the Red Devil mine in Alaska. Material from this location is extremely sought after and practically unavailable on the market.

Care and storage

## Cleaning Due to its extreme rarity and delicacy, mechanical cleaning is absolutely not recommended. Specimens should be left in the condition in which they were found. Any loose debris can be removed very carefully with a soft brush. ## What to Avoid Avoid contact with water, chemicals, and ultrasound. The mineral is susceptible to oxidation in humid air, leading to the formation of a dark tarnish. It should be protected from high temperatures and sudden temperature changes. ## Storage Paradocrasite specimens require storage under stable conditions. They are best placed in a sealed, padded "perky box" or in a display cabinet with controlled humidity, away from direct sunlight and heat sources.

Sources

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