Nikischerite
Chemical formula: NaFe<sup>2+</sup><sub>6</sub>Al<sub>3</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>18</sub>(H<sub>2</sub>O)<sub>12</sub>
Nikischerite is a very rare mineral of the wermlandite group, forming characteristic, tabular crystals with a hexagonal outline and green color.
Description
## Characteristics Nikischerite is a hydrated sulfate of sodium, iron, and aluminum, belonging to the wermlandite group. It is the ferrous (Fe²⁺) analog of magnesium wermlandite. It forms thin to thick, tabular crystals with a distinct, hexagonal outline. These crystals often occur as rosettes, fan-shaped aggregates, or lamellar packets. Its most characteristic visual feature is an intense, green or yellowish-green color. ## Physical Properties This mineral is very soft, with a Mohs hardness of about 2. It exhibits a pearly luster on cleavage surfaces. It is translucent. The calculated density for nikischerite is 2.45 g/cm³. ## Colors and Varieties Nikischerite occurs in shades from green to yellowish-green. No color or commercial varieties are distinguished. ## History and Name The mineral was described in 2002 by D. K. Teertstra, P. C. Piilonen, L. A. Groat, and R. C. Peterson. Its name honors Anthony “Tony” J. Nikischer (born 1953), an American mineral dealer, founder of Excalibur Mineral Corporation, and collector, in recognition of his contributions to mineralogy. The type locality is the Palabana area in Zambia. ## Uses Due to its rarity and small crystal size, nikischerite has no industrial applications. It is solely an object of scientific and collecting interest.
Diagnostic features
## Identification Key features for identifying nikischerite are its characteristic habit in the form of hexagonal, tabular crystals, intense green color, pearly luster on cleavage planes, and very low hardness. Its specific occurrence environment and associated minerals are also important indicators. ## Distinguishing from Similar Minerals Nikischerite can be confused with other green minerals with a tabular or platy habit, such as wermlandite, some chlorites, or micas. From wermlandite, which is its magnesium analog, it usually differs by a more intense, greener color. From micas and chlorites, it is distinguished by the perfectly hexagonal outline of its crystals and the lack of elasticity of the lamellae. Reaction to acids can also be helpful in distinguishing it from some silicates. ## Crystal Forms Nikischerite crystals are tabular, with a hexagonal outline, corresponding to its trigonal symmetry. They occur individually, in parallel intergrowths, and most often form aggregates in the form of rosettes, fans, or lamellar clusters.
Geological environment
## Genesis Nikischerite is a secondary mineral, formed under low-temperature hydrothermal processes. At the type locality in Zambia, it was found in voids within scapolite-phlogopite rocks. ## Mineral Associations This mineral co-occurs with pyrite, pyrrhotite, chalcopyrite, scapolite, phlogopite, and apatite. ## Localities Nikischerite is an extremely rare mineral. The only significant and historically confirmed locality for its occurrence, from which almost all collecting material originates, is its type locality - the Palabana area, Mfuwe district, in Zambia.
Rarity
Very rare
Collector aspects
## Quality Criteria The most highly valued nikischerite specimens are characterized by sharply defined, well-formed crystals with a hexagonal shape. The intensity and saturation of the green color are also important. Particularly sought after are aesthetic compositions, such as perfectly formed crystal rosettes, set on a small rock matrix. The size of the crystals and their aggregates also significantly affects the value. ## Popular Localities The only source of collectible specimens is the type locality in the Palabana area in Zambia. Specimens from this locality are considered classic for this species.
Care and storage
## Cleaning Nikischerite is a very soft and delicate mineral. For dust removal, it is best to use compressed air or a very soft, dry brush. Wet cleaning should be avoided, and if absolutely necessary, distilled water should be used for a very short contact time, immediately drying the specimen. ## What to Avoid As a hydrated sulfate, it is sensitive to high temperatures, which can lead to dehydration and structural damage. Contact with acids and other chemicals should be avoided. Due to its low hardness, it is susceptible to scratches and mechanical damage. ## Storage Nikischerite specimens should be stored in stable conditions, away from heat and moisture sources. The safest way is to keep it in a sealed “membrane box” or in a display case, which protects it from dust, damage, and sudden environmental changes.