Piemontite-(Pb)

Chemical formula: CaPb<sup>2+</sup>(Al<sub>2</sub>Mn<sup>3+</sup>)[Si<sub>2</sub>O<sub>7</sub>][SiO<sub>4</sub>]O(OH)

Piemontite-(Pb) is a rare mineral from the epidote group, a lead analog of piemontite, distinguished by its reddish-brown color and occurrence in manganese deposits.

## Characteristics Piemontite-(Pb) is a lead analog of piemontite, belonging to the epidote group. It forms prismatic, elongated crystals, often with striations along the elongation axis. It typically occurs as radial or fibrous aggregates. Its characteristic feature is an intense, reddish-brown to almost black color. ## Physical Properties This mineral is characterized by a hardness of approximately 6 on the Mohs scale. It has a vitreous luster and is translucent to opaque. The density is relatively high for a silicate, around 4.15 g/cm³, which is a result of the presence of lead in its structure. ## Colors and Varieties The dominant color of piemontite-(Pb) is reddish-brown, which, depending on impurities and crystallization conditions, can range from reddish to black. No commercial or color varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition – it is piemontite in which lead (Pb) predominates. It was formally described and approved by the International Mineralogical Association (IMA) in 2011. The type locality (locus typicus) is the Kombat Mine in Namibia. ## Applications Piemontite-(Pb) has no industrial applications. Due to its rarity and attractive appearance, it is a mineral valued by advanced collectors and scientific institutions.

Properties

Mohs hardness
6
Luster
Vitreous
Streak
Reddish-brown
Density
4.15
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Key diagnostic features include its reddish-brown color, vitreous luster, relatively high density, and characteristic prismatic crystal habit. Its occurrence in association with other manganese and lead minerals in a specific geological environment is a strong indicator. ## Distinguishing from Similar Minerals It can be confused with common piemontite, from which it differs by its significantly higher density and genesis associated with lead-rich deposits. Other similar minerals, such as epidote or allanite, usually have different colors (green, brown, black) and rarely exhibit such an intense red hue. ## Crystal Forms Piemontite-(Pb) forms columnar, prismatic crystals, often elongated and longitudinally striated. It also occurs as radial or fibrous aggregates and clusters.

Geological environment

## Genesis It is a hydrothermal mineral, formed during the metamorphism of manganese and lead ore deposits. It forms in veins cutting through rocks rich in these elements. ## Mineral Associations It co-occurs with other minerals characteristic of this type of environment, such as baryte, hematite, hausmannite, johninnesite, celsian, miankite-(Ce), and its magnesium analog, piemontite-(Mg). ## Localities The most important and best-documented locality for piemontite-(Pb), which is also its type locality, is the Kombat Mine in the Otjozondjupa Region of Namibia. It is also known from the Prabornaz Mine in the Aosta Valley, Italy.

Rarity

Very rare

For collectors

## Quality Criteria The most valued specimens are those with well-formed, sharp crystals of intense, reddish-brown color. The aesthetic composition with associated minerals is also important, especially if they form a contrasting matrix. Crystal size and lack of damage significantly increase collectible value. ## Popular Localities Specimens from the Kombat Mine in Namibia are by far the most sought after by collectors, as this locality has yielded the best crystals of this mineral known to date.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush or paintbrush to remove dust. Due to potential reactivity, contact with water, and especially with acids and detergents, should be avoided. ## What to Avoid Ultrasonic cleaners and all chemical agents that could damage delicate crystals or cause undesirable reactions should be strictly avoided. The mineral is sensitive to sudden temperature changes. ## Storage It is recommended to store specimens in stable conditions, in closed boxes or display cases, away from direct sunlight and humidity. Due to its lead content, hands should be washed after handling the mineral.

Sources

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