The stable form of sulphur at room temperature and normal atmospheric pressure is

Orthorhombic sulphur, abbreviated ${\mathrm{S}}_{\alpha }$, is the most important kind of sulphur. It is stable at room temperature and air pressure in its usual form. There are various names for this allotrope, including rhombic sulphur, Muthmannsulphur I, $\alpha$-sulphur, and orthorhombic sulphur; this name is the one that is most frequently used.