Erenkoy magnesite deposits reside in Eskisehir and Bilecik provinces of northwestern Turkey. Local geology consists of metamorphites of blueschist facies in the base; ophiolitic rocks with mainly serpentinites, peridotites; ophiolitic melanges with a varying range of lithology: cherts, calcschists, blueschist rocks, limestone and on top of all these there are neogene sedimentary units that are mainly consisted of sandstone and clay formations. Magnesite deposits in the area are associated with ultramafic rocks: serpentinites and peridotites. The deposits are shaped as veins and veinlettes, stockworks and lenses primarily however most of them have lost their primary shape due to intense tectonic activity and resulting deformation, therefore sometimes showing irregular masses. The formations of magnesite usually strictly follow discontinuities like fault and crack zones. The magnesites are white colored, cryptocrystalline and mostly have either massive habit, showing conchoidal fractures and dehydration cracks or botryoidal (cauliflower) habit. They show microscopic pinolite textures. Magnesites in the deposits are usually accompanied with dolomites, sepiolites, serpentines, talc, quartz, opal, chalcedony (formed in vugs), iron oxides. Magnesite is also present along with serpentintes, iron oxides, dolomites and silica formations on the surface in extensive weathered and altered parts of the host rocks. Initial geochemical analyses show high SiO2 content in magnesites, Fe2O3 content is also elevated in some samples taken from surface. These indicate to silica and iron oxide formations associated with magnesite deposits. Also elevated CaO content in some samples can be explained by dolomite formations in Magnesite deposits.