Yellow rock
SULFUR is a naturally occurring substance in the earth. It is yellow, soft and lightweight.
Sulfur is a mineral found in limestone rock at/or near crater crevices in volcanic areas, as well as cracks of extinct and active volcanoes. It has been deposited by gases of volcanic origin and the action of hot springs.
Usually bright yellow, it may also be darker. In powdered form, its streak or color is white. A deposit of the chemical element can be found in Pamplona, Negros Oriental province.
Being abundant in native form, sulfur was known in ancient times. A Song Dynasty military treatise of 1044 AD described different formulas for Chinese black powder as a mixture of potassium nitrate, charcoal and sulfur.
Sulfur is also referenced in the Bible as brimstone. Fumes from burning sulfur were used as fumigants. The substance is used chiefly as a process chemical rather than for its sulfur value.
Commercially, the element is primarily used in fertilizers because plants need relatively large amounts of the substance.
Most of sulfur produced is used to make sulfuric acid. The rest is used in fertilizers and many industrial applications, including detergents, synthetic resins, dyestuffs, aluminum reduction, paper sizing and many others.