Cesplumtantite

Chemical formula: Cs₂Pb₂+₃Ta₅+₈O₂₄

Cesplumtantite is an extremely rare, black mineral that is a complex oxide of cesium, lead, and tantalum, known only from a single pegmatite in China.

## Characteristics Cesplumtantite is a black mineral with a submetallic luster. It occurs as anhedral (irregular) to subhedral (poorly formed) grains, not exceeding 1.5 mm in size. It is completely opaque. Due to its microscopic nature, its visual features are difficult to observe without magnification. ## Physical Properties The mineral's hardness is estimated at approximately 7 on the Mohs scale. It is a dense mineral, with a calculated density of 7.81 g/cm³. It exhibits an uneven fracture, and cleavage has not been observed in the studied samples. ## Colors and Varieties The mineral is uniformly black. No color varieties or commercial varieties have been distinguished. ## History and Name The name "cesplumtantite" is derived from its three key chemical components: cesium (Latin: *caesium*), lead (Latin: *plumbum*), and tantalum. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2020. Its discovery took place in the Man-gong-zhang pegmatite, in the Nanping pegmatite field (Fujian Province, China). ## Applications As a mineral of extreme rarity and microscopic size, cesplumtantite has no industrial applications. Its significance is purely scientific and collectible, being a subject of interest for specialized systematic collections.

Properties

Mohs hardness: 7
Luster: Submetallic
Streak: Blackish brown
Density: 7.81
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of cesplumtantite based on visual characteristics is impossible. This mineral is indistinguishable from other black oxides without advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) and X-ray diffraction (XRD), which can confirm its unique chemical composition with high cesium, lead, and tantalum content. ## Distinguishing from Similar Minerals It can be confused with other black, heavy pegmatite minerals, such as tantalite, columbite, or minerals from the microlite group. The key distinguishing feature is the unique combination of elements (Cs-Pb-Ta), which can only be demonstrated by chemical analysis. ## Crystal Forms It occurs as anhedral or poorly formed grains. Well-formed, euhedral crystals have not yet been described.

Geological environment

## Genesis Cesplumtantite forms under conditions of extreme elemental fractionation in highly albitized core zones of lithium-cesium-tantalum (LCT) pegmatites, lepidolite type. Its presence indicates a very advanced stage of magmatic evolution. ## Mineral Associations It co-occurs with quartz, albite, lepidolite, tantalite-(Mn), and pollucite. ## Localities The only confirmed locality in the world is the type locality – the Man-gong-zhang pegmatite in Nanping, Fujian Province, China.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare micromineral, the most important criterion is certainty of identification, confirmed by analysis. The value of a specimen is increased by the size of the cesplumtantite grains and their abundance on the rock matrix. The aesthetics of the specimen itself are of secondary importance. ## Popular Localities The only source of specimens is the type locality in China. Availability on the collector's market is practically zero, and any specimens are found in research institutions and a few specialized systematic collections.

Care and storage

## Cleaning Cesplumtantite specimens, usually in the form of microscopic grains on a matrix, should be cleaned with the utmost care. The safest method is to gently remove dust with a stream of air from a photographic blower. Avoid wet cleaning and the use of any brushes. ## What to Avoid The mineral is sensitive to mechanical methods. Ultrasonic cleaners, chemical agents, high temperatures, and friction should be absolutely avoided. Any attempt at invasive cleaning risks the loss or damage of microscopic crystals. ## Storage The best way to store it is in a specialized "micromount" box, which protects the specimen from dust, shocks, and physical contact, while allowing for observation under a microscope.

Sources

IMA Mineral List (CNMNC)