Magnesium silicate modified with hexadecyltrimethylammonium cations was synthesized by mechanochemical treatment of a mixture of magnesium hydroxide, silica xerogel, lithium fluoride, and hexadecyltrimethylammonium bromide. The X-ray diffraction analysis, scanning electron microscopy, and differential scanning calorimetry examinations and thermogravimetric analysis showed that variation of the synthesis conditions led to the formation of products differing both in the degree of structural order and in the particle size. Keywords: organically modified magnesium silicate, mechanochemical synthesis, hexadecyltrimethylammonium bromide Layered silicates modified with cationic surfactants are promising sorbents for water and soil purification [1, 2] and precursors for preparation of mesoporous materials [3]. Organically modified layered silicates are currently used as rheological additives in drilling fluids and greases, as well as in the manufacture of inorganic polymer compositions, paints and varnishes, and cosmetics [2][3][4][5].