Zinconigerite-6<i>N</i>6<i>S</i>

Chemical formula: Zn<sup>2+</sup><sub>3</sub>Sn<sup>4+</sup><sub>2</sub>Al<sub>16</sub>O<sub>30</sub>(OH)<sub>2</sub>

Zinconigerite-6N6S is an extremely rare mineral from the nigerite group, a zinc-tin oxide with a complex structure, found in granitic pegmatites.

## Characteristics Zinconigerite-6N6S is an extremely rare mineral belonging to the nigerite group. It forms very small, hexagonal, tabular crystals, usually not exceeding 0.5 mm in size. It most often occurs as inclusions in other minerals, such as quartz, muscovite, or gahnospinel. Its crystals are too small to assess their visual characteristics with the naked eye. ## Physical Properties Due to its extreme rarity and microscopic crystal size, most physical properties have not been fully studied. Hardness is estimated at about 8 on the Mohs scale, which is typical for minerals in this group. Luster is described as vitreous to metallic. ## Colors and Varieties Observed crystals range in color from dark brown to black. No varieties of this mineral have been distinguished. ## History and Name The mineral was approved by IMA in 2018 (IMA2018-033). Its name refers to its chemical composition – the dominance of zinc (zinco) – and its relation to the nigerite structure. The "-6N6S" suffix describes a specific, complex polymorphic type (polytypoid) of its crystal structure. It was discovered in material from the Nová Ves pegmatite near Český Krumlov in the Czech Republic.

Properties

Mohs hardness
8
Luster
Vitreous to metallic
Streak
Light brown
Density
4.65
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Opaque
Crystal system
Trigonal

Diagnostic features

## Identification Identification of zinconigerite-6N6S is impossible without advanced laboratory techniques. It requires chemical analysis (EDS) to confirm the presence of zinc and tin, and electron diffraction (EBSD) or X-ray diffraction to determine its unique crystal structure. It occurs as very small, hexagonal, tabular crystals within the host rock. ## Distinguishing from Similar Minerals It can be confused with other minerals from the nigerite group (such as nigerite, zinconigerite-2N1S) and similar oxides, such as gahnospinel, hercynite, or magnetite. Differentiation is possible only based on precise chemical composition and crystal structure analysis. ## Crystal Forms It forms small, hexagonal, tabular crystals.

Geological environment

## Genesis Zinconigerite-6N6S forms in granitic pegmatites rich in lithium, phosphorus, and fluorine. It is a hydrothermal phase mineral, crystallizing in the late stage of pegmatite evolution, under conditions of elevated zinc and tin activity. ## Mineral Associations It co-occurs with minerals such as quartz, muscovite, gahnospinel (zinc-rich blue spinel), cassiterite, triphylite, zwieselite, apatite-(CaF), and zincite. ## Localities The only confirmed locality of this mineral in the world (type locality) is the pegmatite in Nová Ves, located north of Český Krumlov in the South Bohemian Region, Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, zinconigerite-6N6S is not evaluated according to typical aesthetic criteria. The collector's value of a specimen lies in the confirmed presence of the mineral through analysis. The most valuable are fragments of host rock with the largest possible number of identified microcrystals, well-documented analytically, and originating from the type locality.

Care and storage

## Cleaning Due to the microscopic size and occurrence as inclusions, zinconigerite-6N6S specimens do not require and are not amenable to cleaning. Any attempt at mechanical or chemical intervention would destroy the delicate rock material in which the mineral is found. ## What to Avoid Avoid all chemicals, ultrasonics, and sudden temperature changes. The specimen should be protected from mechanical damage and abrasion. ## Storage Specimens containing zinconigerite-6N6S should be stored in stable conditions, in sealed "micromount" boxes, to protect them from dust and damage. It is best to keep them away from direct sunlight and heat sources.

Sources

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