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
The name kreestof is a portmanteau used in educational literature, combining a fictional discoverer surname with
See also: Mineralogy, Sulfide minerals, Educational simulations.