Sulfur

Hardness: 1.5–2.5 (Mohs scale); Color: Bright yellow to greenish-yellow; Luster: Resinous to adamantine; Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 2.07.

Primary formation occurs via sublimation from volcanic gases or precipitation from hydrothermal fluids. It also forms as a secondary mineral through the bacterial breakdown of sulfate minerals (like gypsum) in sedimentary salt dome environments. Native sulfur can be found in deposits ranging from modern to ancient geological ages.

Used extensively in the chemical industry for producing sulfuric acid, fertilizers, gunpowder, matches, and insecticides. In medicine, it is used in dermatological treatments. While too soft for jewelry, high-quality crystal clusters are highly prized by mineral collectors.

Sulfur is known as 'brimstone' in historical and religious texts. It has a very low melting point (115.21°C) and can emit a faint odor of rotten eggs when reacted or heated, though pure sulfur is odorless.

Identify in the field by its distinct bright yellow color, extreme brittleness, and low density. It often occurs near volcanic vents (fumaroles) or as crusts on sedimentary rocks. Major locations include Sicily (Italy), the Gulf Coast of the US, and volcanic regions like the Andes and Indonesia.