Naquite
Chemical formula: FeSi
Naquite is an extremely rare mineral, an iron silicide, occurring as microscopic inclusions in native iron.
Description
## Characteristics Naquite is an iron silicide with a metallic character. It occurs as anhedral, irregularly shaped grains, usually not exceeding 0.1 mm in size. It typically forms inclusions within native iron. Due to its microscopic size, its visual characteristics can only be examined under a microscope in reflected light, where it appears as a grayish-white, isotropic mineral. ## Physical Properties This mineral is characterized by a strong metallic luster and is opaque. Its density, calculated based on its chemical composition and unit cell parameters, is 6.13 g/cm³. Its hardness has not been precisely determined. ## Colors and Varieties Naquite has a consistent, grayish-white color with a metallic luster. No color varieties or commercial forms are known. ## History and Name Naquite was recognized as a new mineral by the International Mineralogical Association (IMA) in 1982, and its description was published in 1984. The name is derived from the acronym of the Chinese research institute NAnjing GAI-kuang Research Institute, where its analysis was conducted. ## Applications Due to its extreme rarity and microscopic size, naquite has no commercial or industrial applications. It is solely an object of scientific interest, serving as an important indicator of specific, reducing conditions of rock formation.
Diagnostic features
## Identification Identification of naquite is impossible without advanced analytical equipment. It requires chemical analysis using an electron microprobe (EDS or WDS) to confirm its composition (FeSi). In microscopic studies in reflected light, it is grayish-white and isotropic (shows no color changes when the stage is rotated). ## Distinguishing from Similar Minerals Naquite can be confused with other rare minerals occurring in association with native iron, such as cohenite ((Fe,Ni,Co)₃C) or schreibersite ((Fe,Ni)₃P). Definitive differentiation is only possible based on chemical composition analysis, as their optical properties can be similar. ## Crystal Forms Naquite forms only microscopic, irregular grains (anhedral forms) ranging in size from a few to one hundred micrometers.
Geological environment
## Genesis Naquite forms under strongly reducing conditions, with very low oxygen activity. Its genesis is associated with processes occurring within gabbro-diabase intrusions, where crystallization of native iron and associated silicides, carbides, and phosphides took place. ## Mineral Associations This mineral occurs almost exclusively in paragenesis with native iron (as inclusions). It is also accompanied by other minerals typical of this environment, such as wüstite, cohenite, schreibersite, magnetite, ilmenite, and weathering products, e.g., goethite. ## Localities The only confirmed locality of naquite in the world is its type locality – the Jianshan iron ore deposit in He County, Anhui Province, China.
Rarity
Extremely rare
Collector aspects
## Quality Criteria Naquite is not a collector's mineral in the common sense. It does not form macroscopic specimens. Its value is purely scientific. In specialized collections, the "quality" of a specimen is defined by the richness of the mineral association visible in the polished section and the quality of the microscopic preparation itself. ## Popular Localities The only source of material for research is the type locality in China. The mineral is not available on the collector's market.
Care and storage
## Cleaning Due to its occurrence as microscopic inclusions in other minerals, naquite specimens are not subject to cleaning in the traditional sense. They are examined exclusively as professionally prepared metallographic polished sections. ## What to Avoid Specimens containing naquite (usually polished samples) should be protected from moisture and aggressive chemicals that could damage the surrounding minerals, especially native iron, which is susceptible to oxidation. ## Storage Naquite samples, most often in the form of resin-embedded discs (polished sections), should be stored in a dry place, preferably in specialized boxes that protect the polished surface from scratches and dust.