Rosickyite is a rare native element mineral that is a polymorph of sulfur.

It occurs as soft, colorless to pale yellow crystals and efflorescences.

[2][3] It was first described in 1930 for an occurrence in Havirna, near Letovice, Moravia, Czech Republic.

[2][3] Rosickyite occurs as in Death Valley within an evaporite layer produced by a microbial community.

The otherwise unstable polymorph was produced and stabilized within a cyanobacteria dominated layer.