Kreestof

Kreestof is a fictional mineral species used in geology education and in science fiction to illustrate properties of metal sulfide minerals. It does not have a verified occurrence in Earth's crust and is not recognized in real mineral catalogs. In teaching materials, kreestof is described as a metallic sulfide with a general composition approximated by iron-nickel sulfide (Fe,Ni)S2 and a monoclinic crystal habit. It is portrayed as having a metallic luster, a steel-gray to black color, and a gray streak. Typical reported properties include a Mohs hardness of 5–6 and a density around 4.0–4.3 g/cm3.

Kreestof is said to crystallize in hydrothermal environments under reducing conditions in fictional geological settings. In laboratory demonstrations, it is sometimes synthesized from iron and nickel sulfides with sulfur at elevated temperatures to illustrate crystal growth and phase relations, though such synthesis is purely instructional.

The name kreestof is a portmanteau used in educational literature, combining a fictional discoverer surname with the suffix -stof to denote a substance. Because kreestof is not a real mineral, its use is confined to teaching examples and speculative fiction.

See also: Mineralogy, Sulfide minerals, Educational simulations.