In Soroako, Sulawesi, Dietrich Drescher melted iron from limonite, that has presumably been used for the famous Toraja / Bugis blades and keris in the Majapahit era. Limonite is an iron ore consisting of a mixture of hydrated iron oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the three principal iron ores, the others being hematite and magnetite, and has been mined for the production of iron since at least 2500 BCE.
Limonite is named from the Greek word for meadow in allusion to its occurrence as bog iron ore in meadows and marshes. By the way, the word may also originate from the Latin „limus“ – which means mud – or in its yellowish lemon-like color. In its brown form, it is sometimes called brown hematite or brown iron ore. In its bright yellow form, it is sometimes called lemon rock or yellow iron ore.
Soroako, also spelled Sorowako, is a small mining town in the north-east of South Sulawesi province, in the center of Sulawesi island. It is the location of the Sorowako Mine, which is the largest open-pit mine in Indonesia, owned by PT Inco, a subsidiary of the Canadian-based mining company Vale Inco. Soroako is surrounded by three natural lakes: Lake Matano, Lake Towutiand Lake Mahalona. Matano Lake is the deepest lake in Indonesia.
In the limonite deposits of the Toraja highlands around Lake Matano, also nickel-ferrous varieties occur, which have been used for blades for many centuries. Dietrich Drescher made samples and Kris blades out of these and used pure nickel pellets for pamor experiments.