Papikeite

Chemical formula: NaFe<sup>2+</sup><sub>2</sub>(Mg<sub>3</sub>Al<sub>2</sub>)(Si<sub>5</sub>Al<sub>3</sub>)O<sub>22</sub>(OH)<sub>2</sub>

Papikeite is a very rare mineral from the amphibole group, named after the mineralogist James J. Papike.

## Characteristics Papikeite is an extremely rare mineral belonging to the sodium amphibole group. It has been identified in the form of microscopic, prismatic crystals up to 100 micrometers long, forming aggregates within the host rock. Due to the size of the crystals, its macroscopic features are not well understood. ## Physical Properties The crystals exhibit strong pleochroism, changing color from pale yellow to dark blue depending on the observation direction. Hardness and density have not been precisely measured but are estimated based on the properties of other amphiboles. ## History and Name The mineral was approved by the International Mineralogical Association (IMA) in 2014. Its name honors James J. Papike (1937–2020), a distinguished American mineralogist and geochemist, for his contributions to the study of rock-forming minerals, including amphiboles.

Properties

Mohs hardness
5-6
Luster
Vitreous
Streak
Pale blue
Density
3.25
Cleavage
Perfect on {110}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of papikeite is possible only through advanced laboratory techniques, such as electron microprobe analysis (EMPA) for chemical composition and X-ray diffraction (XRD) for crystal structure determination. Its unique chemical composition and strong pleochroism in polarized light are characteristic features. ## Differentiation from Similar Minerals It can be confused with other sodium amphiboles, such as riebeckite or crossite, with which it coexists. Differentiation requires precise chemical analysis, especially of magnesium and aluminum content at specific positions in the crystal structure. ## Crystal Forms It forms elongated, prismatic crystals, occurring as small aggregates or individual inclusions within the rock.

Geological environment

## Genesis Papikeite forms under conditions of low-temperature and high-pressure metamorphism. It was discovered in crossite schists, which are part of an ophiolite complex – a fragment of ancient oceanic crust that underwent subduction and was subsequently uplifted to the surface. ## Mineral Associations This mineral coexists with other minerals typical of the glaucophane schist facies, such as crossite, albite, quartz, stilpnomelane, piemontite, titanite, and hematite. ## Localities The only confirmed locality of papikeite in the world (type locality) is the Sorkun area near the village of Mihalıççık in Eskişehir Province, Turkey.

Rarity

Extremely rare

For collectors

## Quality Criteria Papikeite is not a collectible mineral in the traditional sense. Its value is purely scientific. Specimens consist of microscopic inclusions in rock and do not possess aesthetic qualities. The only criterion is the confirmation of the mineral's presence through laboratory analyses.

Care and storage

## Cleaning Due to the extreme rarity and microscopic nature of the specimens, standard cleaning methods are not applicable. Specimens should only be analyzed under laboratory conditions. ## What to Avoid Avoid all chemicals, ultrasonics, temperature changes, and moisture. Any attempt at cleaning outside a specialized laboratory risks irreversible destruction of the type material. ## Storage Papikeite specimens, being research material, are stored in specialized containers under stable temperature and humidity conditions, protected from light and vibrations.

Sources

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