Antimonilla

Antimonilla is a hypothetical mineraloid, a naturally occurring substance that resembles a mineral but lacks a definite crystalline structure. It is described as a type of antimony sulfide, with its chemical composition varying due to its amorphous nature. The name "antimonilla" is derived from antimony, the primary element it contains, and the suffix "-illa," which often denotes a lesser or imitative substance.

While not formally recognized by mineralogical authorities due to its lack of a defined crystal lattice, antimonilla has been discussed in historical geological contexts as a potential end-member in the spectrum of antimony-bearing amorphous deposits. Its formation is thought to be associated with hydrothermal processes where antimony-rich fluids cool rapidly, preventing the organized crystallization of typical antimony sulfide minerals like stibnite. The appearance of antimonilla is generally described as amorphous, often presenting as earthy masses or powdery aggregates, typically with a dull luster. Its color can range from dark gray to black, depending on the presence of impurities. The physical properties, such as hardness and density, are inconsistent and less defined compared to crystalline minerals. The study of antimonilla primarily falls within the realm of historical mineralogy and the understanding of mineral formation processes.