chalcopyrite

This term is used primarily within the specialized registers of geology, mineralogy, and mining. It describes a specific chemical compound (CuFeS2) and is characterized by a distinct metallic luster and brassy hue, which often leads to it being mistaken for gold by amateur prospectors, earning it the colloquial nickname "fool's gold" alongside pyrite.

As a technical mineralogical term, it is treated as an uncountable mass noun when referring to the substance in general. While it can be used countably when referring to specific mineral specimens or distinct types of chalcopyrite variants, it is most frequently encountered as an uncountable noun in scientific descriptions of ore deposits.