Dietrich Drescher made iron from ore which he collected from a Jarosite deposite in Sariater, Eastern Java. Jarosite is a basic hydrous sulfate of potassium and iron with a chemical formula of KFe3+3(OH)6(SO4)2. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides.
Jarosite is often produced as a byproduct during the purification and refining of zinc and is also commonly associated with acid mine drainage and acid sulfate soil environments. It is usually found in combination with realgar(Sulphur arsenic), used for color-etching of keris-blades.