Most of the sepiolite of commerce is obtained chiefly from the plain of Eskişehir in Turkey, between Istanbul and Ankara. It occurs there in irregular nodular masses, in alluvial deposits, which are extensively worked for its extraction. It is said that in this district, there are 4000 shafts leading to horizontal galleries for extraction of the sepiolite. The principal workings are at Sepetçi Ocağı and Kemikçi Ocağı, about 20 miles southeast of Eskişehir. The mineral is associated with magnesite (magnesium carbonate), the primitive source of both minerals being a serpentine.