Pohlite

Chemical formula: Pb₂+₇(I₅+O₃)(OH)₄Cl₉

Pohlite is an extremely rare lead iodate with chlorine and hydroxyl groups, forming small, tabular, yellow crystals.

## Characteristics Pohlite is a very rare secondary mineral from the iodate group. It occurs as very small, thin, tabular crystals with a hexagonal outline, usually not exceeding 0.2 mm. These crystals often form rosette-like or randomly oriented aggregates on the surface of the host rock. Due to its chemical composition, containing lead and iodine, it is an object of scientific interest. ## Physical Properties Pohlite crystals exhibit a bright yellow color and a pale, yellowish-white luster. They are transparent to translucent. Due to the microscopic size of the crystals, precise determination of hardness and density is impossible; however, the density calculated based on the formula and unit cell parameters is 6.55 g/cm³. ## History and Name The mineral was named in honor of Demetrius Pohl (born 1942), a German physicist and crystallographer, in recognition of his contribution to research on minerals from the Chilean iodate group. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2011. The type locality is the Casualidad mine in the Tarapacá region, Chile. ## Uses Pohlite has no industrial application. Its significance is purely scientific and collectible, as an extremely rare mineral typical of the unique oxidation zones of nitrate deposits in Chile.

Properties

Luster: Resinous to pearly
Streak: Light yellow
Density: 6.55
Cleavage: Perfect on {0001}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of pohlite is practically possible only through advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to the microscopic size of the crystals. Visually, it is characterized by a bright yellow color and occurrence in the form of small, tabular crystals forming rosette-like aggregates. ## Distinguishing from Similar Minerals It can be confused with other secondary, yellow lead or iodine minerals occurring in the same environment, such as seeligerite or schwartzembergite. Certain differentiation requires chemical analysis (EDS) to confirm the presence of iodine, lead, and chlorine in appropriate proportions. ## Crystal Forms Pohlite forms thin, tabular crystals with a hexagonal outline. These crystals occur individually or more often as rosette-like, fan-shaped, or irregular aggregates on the surface of the host rock.

Geological environment

## Genesis Pohlite is a secondary mineral, formed in the oxidation zones of iodine-bearing deposits. Its genesis is associated with the weathering processes of primary minerals in extremely arid (desert) climatic conditions, typical of the Atacama Desert in Chile. ## Mineral Associations It occurs in association with other rare iodate and chloride minerals, such as seeligerite, schwartzembergite, iodyrite, and hematite. ## Localities The only confirmed locality for pohlite worldwide is its type locality - the Casualidad mine, Zapiga district, Iquique province, Tarapacá region in northern Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" type mineral, the collector's value of pohlite depends on the richness and aesthetics of the crystal aggregates on the rock matrix. Specimens with clearly formed, sharp crystals forming dense, rosette-like clusters are most prized. The intensity of the yellow color and good contrast with the substrate also increase the attractiveness of the specimen. Due to its extreme rarity, any specimen with confirmed identity is considered very valuable. ## Popular Localities The only source of pohlite specimens is the Casualidad mine in Chile. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically.

Care and storage

## Cleaning Due to its extreme rarity, small size, and potential fragility, pohlite specimens should not be cleaned mechanically or chemically. Any attempts at cleaning may destroy the delicate crystals. If dust removal is necessary, use only compressed air from a safe distance. ## What to Avoid Avoid contact with water, acids, chemical agents, and ultrasound. The mineral is likely sensitive to changes in temperature and humidity. Do not expose it to direct sunlight, which may cause fading. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes to protect them from dust, mechanical damage, and humidity changes. Store in stable room conditions, away from heat and light sources.

Sources

IMA Mineral List (CNMNC)