Yedlinite

Chemical formula: Pb₂+₆Cr₃+Cl₆O(OH)₇

Yedlinite is an extremely rare lead and chromium mineral, forming characteristic, hexagonal crystals of an intense red color.

## Characteristics Yedlinite is a complex lead and chromium oxyhalide, recognizable by its unique, hexagonal crystals. It typically forms small, prismatic or tabular crystals that may show elongation along the crystallographic axis. Its most characteristic features are its intense, dark red to reddish-purple color and a strong, almost metallic luster, which makes it a visually striking mineral despite the small size of its crystals. ## Physical Properties This mineral has a hardness of approximately 3 on the Mohs scale. It exhibits a high luster, described as submetallic to adamantine. It is a heavy mineral due to its high lead content, with a density of about 6.15 g/cm³. Crystals are usually opaque, with translucency only visible on thin edges. ## Colors and Varieties Yedlinite occurs in a characteristic range of colors from dark red, through reddish-purple, to almost black. No named varieties of this mineral have been distinguished. ## History and Name The mineral is named in honor of Leo Yedlin (1914-1977), an American mineral and micromineral collector from New Haven, Connecticut, who first discovered this mineral. Yedlinite was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 1974. Type specimens come from the Mammoth-St. Anthony Mine in Tiger, Pinal County, Arizona, USA. ## Uses Due to its extreme rarity and small crystal size, yedlinite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals and microminerals.

Properties

Mohs hardness: 3
Luster: Submetallic to adamantine
Streak: Reddish-brown
Density: 6.15
Cleavage: None
Fracture: Conchoidal
Transparency: Opaque, translucent on thin edges
Crystal system: Trigonal

Diagnostic features

## Identification The most important diagnostic features of yedlinite are its characteristic hexagonal crystal shape, intense dark red color, high luster (submetallic to adamantine), and reddish-brown streak. Its occurrence in association with other rare secondary minerals in the oxidation zone of lead deposits is also a key indicator. ## Distinguishing from Similar Minerals Due to its unique appearance and composition, yedlinite is difficult to confuse with other minerals, especially when its paragenesis is considered. It may sometimes resemble some dark red varieties of vanadinite, but vanadinite usually has a lighter streak (white to yellowish). Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms Yedlinite crystallizes in the trigonal system, forming hexagonal-shaped crystals. Most commonly, these are short, prismatic or thick tabular crystals, terminated by flat basal faces (pinacoid). It occurs as single, well-formed crystals, rarely in small groups.

Geological environment

## Genesis Yedlinite is a secondary mineral, forming in the oxidation zones (gossans) of hydrothermal lead ore deposits. Its formation requires specific geochemical conditions, including the presence of lead, chromium, and a high concentration of chlorine. Chromium likely originates from the weathering of chromite or other minerals containing this element. ## Mineral Associations This mineral co-occurs with a number of other, often rare, secondary minerals. At its type locality (Mammoth-St. Anthony Mine), it has been found in association with diaboleite, boleite, wulfenite, cerussite, anglesite, phosgenite, hematite, and quartz, among others. ## Localities The only confirmed and well-documented occurrence of yedlinite in the world is the Mammoth-St. Anthony Mine in Tiger, Pinal County, Arizona, USA. This is a so-called "local-type mineral" – a mineral known only from one locality.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a yedlinite specimen is primarily assessed based on the development and size of its crystals. The most desirable are sharp, well-formed, undamaged crystals with a distinct hexagonal outline. The intensity and depth of the red color also increase the specimen's value. A contrasting placement on a rock matrix, especially in association with other rare minerals, is highly prized by collectors. ## Popular Localities The only source of yedlinite specimens is its type locality – the historic Mammoth-St. Anthony Mine in Tiger, Arizona. This mine is currently inactive and inaccessible, meaning no new specimens are entering the market. All available specimens come from old collections.

Care and storage

## Cleaning Yedlinite specimens should be cleaned with the utmost care, preferably using compressed air to remove dust. If wet cleaning is necessary, use only distilled water and a very soft brush, avoiding vigorous rubbing. After cleaning, the specimen should be thoroughly dried immediately. ## What to Avoid As a lead-containing mineral, yedlinite is toxic – avoid inhaling dust and wash hands after any contact. Avoid contact with acids and other chemicals that may damage it. The mineral is relatively soft and brittle, so it must be protected from impacts and scratches. It should not be heated or exposed to prolonged strong light. ## Storage Yedlinite specimens, typically microminerals, are best stored in specialized "micromount" boxes, which protect them from dust and mechanical damage. Due to lead toxicity, it should be stored out of reach of children and pets, preferably in a locked display cabinet.

Sources

IMA Mineral List (CNMNC)