Sulfur is an element that occasionally occurs in elemental form. Typically it occurs as a polyanion with oxygen or in the sulfide form. There are several polymorphs of native sulfur. This is the rhombic version.

Occurrence and Use
Native sulfur occurs in strong reducing conditions, typically associated with hydrothermal activity. It may be found around hot springs and thermal pools, and in massive beds. It will oxidize in an aerated environment, releasing large quantities of acidity. This feature has been exploited for horticultural and agricultural purposes. Incorporation of elemental sulfur in soils causes a release of acidity and a decrease in pH over time.

Wyckoff, R.W.G. 1963. Crystal Structures 1:33.