The gneiss is a metamorphosed (recrystallised) rock, formed under high temperature and pressure conditions. It is foliated, crystallized, composed of minerals like quarzite, feldspar (the most important mineral in rocks) and mica. It can be golden, dark green, silverish, brown and multicoloured, however, the shiny surface is mostly characteristic of the lighter tones. Its bright colours, structure and durability make the gneiss one of the most popular natural interior and exterior cladding stones. We use it mostly for vertical wall cladding. The gneiss can be acquired in irregular (raw) or cut-to-size, 1-3 cm thick blocks. Its maintainance and impregnation should be done with a specially improved stone-protecting and damp-proof sealer, which can be transparent or milk-like. Using this sealer we can offer proper protection to our natural stones against the damaging effects of water.