Xitieshanite
Chemical formula: Fe<sup>3+</sup>S<sup>6+</sup>O<sub>4</sub>Cl·6H<sub>2</sub>O
Xitieshanite is a rare, water-soluble iron sulfate, forming pale yellow, fibrous or acicular crystals in the oxidation zones of sulfide deposits.
Properties
- Mohs hardness
- 2
- Luster
- Silky
- Streak
- Light yellow
- Density
- 1.85
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Xitieshanite can be identified by its characteristic form – delicate, acicular or fibrous aggregates with a pale yellow color and silky luster. A key diagnostic feature is its water solubility. It occurs in dry, desert conditions as a product of sulfide mineral weathering. ## Distinction from Similar Minerals Xitieshanite can be confused with other secondary iron sulfates, such as melanterite, halotrichite, or copiapite. It is distinguished from them by its specific chemical composition (presence of chlorine), and often also by its hue and aggregate form. However, definitive differentiation requires advanced chemical analyses (EDS) or X-ray diffraction (XRD). ## Crystal Forms Xitieshanite crystals are elongated, acicular or fibrous. They typically form radial or tangled aggregates, as well as crusts and efflorescences on rock surfaces.
Geological environment
## Genesis Xitieshanite is a secondary mineral, formed by the oxidation (weathering) of sulfide deposits, especially pyrite and marcasite, in the presence of chloride-rich solutions. It forms in dry and desert conditions, as a product of contemporary weathering processes or as a post-mining mineral in dumps and old mine workings. ## Mineral Associations It co-occurs with other secondary sulfates and minerals of the oxidation zone, such as copiapite, melanterite, halotrichite, gypsum, epsomite, as well as with pyrite and marcasite, from which it originates. ## Localities The most important occurrences of this rare mineral are its type locality – the Xitieshan Pb-Zn deposit in Qinghai (China). It has also been reported in the San Telmo mine in Spain and in several locations in Chile, including the Chuquicamata and El Teniente mines.
Rarity
Rare
For collectors
## Quality Criteria For collectors, the most desirable specimens are those with rich, well-formed aggregates of acicular or fibrous crystals of an intense, pale yellow color. The abundance of the mineral on the rock matrix and aesthetic associations with other secondary minerals are also highly valued. Due to its delicacy, specimens undamaged during collection and transport are rare. ## Popular Localities The most classic and prized specimens come from the type locality in China (Xitieshan). Specimens from other confirmed localities, such as those in Chile or Spain, are also sought after by collectors specializing in mineral systematics.
Care and storage
## Cleaning The mineral is water-soluble, so **it must not be cleaned wet**. To remove dust, a very soft brush or compressed air from a safe distance can be used very carefully. ## What to Avoid Contact with water, water vapor, and high humidity, which can dissolve or damage the specimen, must be strictly avoided. Chemicals, ultrasonics, and high temperatures should also be avoided. ## Storage Xitieshanite specimens must be stored in a dry place, preferably in a sealed, airtight box (a "perky box") or in a display cabinet with a moisture absorber (e.g., silica gel). Protect from dust and mechanical damage.