What does pyrrhotite mean?
Pyrrhotite is a metallic, iron sulfide mineral whose formula is more accurately written Fe₁₋ₓS, indicating that its iron content varies. It is usually recognized by its brassy or bronze-yellow color, metallic lustre, and magnetic character. The mineral commonly forms in igneous and metamorphic rocks, especially where sulfur-rich, high-temperature mineral systems operated, and it may coexist with other sulfide ores such as chalcopyrite and pyrite. From a practical standpoint, pyrrhotite can complicate ore processing because its magnetic and chemical properties differ from those of associated minerals. It is also a term of some interest in planetary science because related or historically associated forms of iron sulfide occur in meteorites. Although “fool's gold” is sometimes used informally for brassy metallic minerals, pyrrhotite should not be confused with pyrite: the two are chemically distinct, and the variable iron content of pyrrhotite is central to its identification and classification.
nounPyrrhotite is an iron sulfide mineral with the variable formula Fe₁₋ₓS. It is typically brass- or bronze-yellow, commonly occurs in igneous and metamorphic rocks, and is often attracted to a magnet.
- A variable-composition iron sulfide mineral, generally brass- or bronze-yellow, that commonly occurs in igneous and metamorphic rocks and is typically magnetic.
"The ore contained microscopic grains of pyrrhotite that were difficult to separate from the associated chalcopyrite."
"Pyrrhotite was identified by its unusual magnetic response during the examination of the rock sample."
"Excess sulfur in the melt allowed pyrrhotite to crystallize alongside chalcopyrite and other sulfide minerals."
The plural is grammatically standard but uncommon because references are usually to the mineral as a mass noun or to individual grains, specimens, or occurrences.
"Several distinct pyrrhotites were recovered from the drill core."
Pyrrhotite carries two visual clues to its identity: a brassy metallic sheen and an attraction to magnets.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of pyrrhotite
The name combines Ancient Greek pyr, meaning “fire,” with rhotos, meaning “streaked,” traditionally interpreted as an allusion to the mineral's fiery, brassy appearance. The compound was adopted as a mineral name in the 19th century. Its first element belongs to a productive Greek family represented in English by words such as pyrite, pyrogen, and pyromorphite.
Related word forms
How pyrrhotite is actually used
This is primarily a specialist geological and metallurgical term. In mineralogy, it may refer to the mineral or to its broader group of crystal structures, and discussions of composition can be technically detailed.
Easily confused with pyrrhotite
Pyrrhotite is an iron-deficient sulfide with variable composition, whereas pyrite is the iron disulfide mineral with the formula FeS₂.
Troilite is a specific form of iron sulfide commonly found in meteorites, while pyrrhotite is the broader name for iron-deficient FeS and may occur in several crystal structures.
Pyrrhotite is an iron sulfide, whereas magnetite is an iron oxide with the formula Fe₃O₄.