The element sulfur is found in salt domes and is also found in volcanic rock, at hot springs and even in meteorites.
Sulfur has a deep yellow color which is one of its unique physical properties. Because sulfur can combine with other elements, it can be found in various forms, including galena, cinnabar, gypsum, and many others.
It produces a yellow streak when it undergoes a streak test and has a strong yellow color unless there are impurities, in which case it can be reddish or greenish.
Using its color is a method of identifying sulfur in the field, along with its hardness of only 2 and its odor when it combines with water (some of it produces hydrogen sulfide gas--which smells like rotten eggs).
Sulfur is yellow is because yellow wavelengths of light are reflected or transmitted to the eyes and we perceive this element as the color yellow. All other wavelengths of visible light are absorbed by the material. The yellow color is an identifier of sulfur, which was known as brimstone in ancient times. When it burns, it emits a blue light.
Sulfur is an important element found in various compounds including proteins, penicillin, and pollutants that cause acid rain.