Sulfur

The Sulfur is an item in Pixark.

Crafting
Used to make Gunpowder (along with fire powder and charcoal) in the Mortar & Pestle.

Additional notes

 * Seems to be able to be found in large deposits on surface of swamps.
 * The in-game descriptions use the American spelling of "Sulfur" while the game files use the British spelling of "Sulphur".