The present invention relates to an effect pigment comprising as a substrate a glass flake with a coating, said coating comprising at least one layer of at least one high refractive material, said material having a refractive index of at least 1.8, and/or at least one layer of at least one semitransparent metallic material, wherein said glass flakes comprising the following composition: 65 - 75 wt.-% silicon oxide, preferably SiO 2 2 - 9 wt.-% aluminium oxide, preferably Al 2 O 3 0.0 - 5 wt.-% calcium oxide, preferably CaO 5 - 12 wt.-% sodium oxide, preferably Na 2 O 8 -15 wt.-% boron oxide, preferably B 2 O 3 0.1 - 5 wt.-% titanium oxide, preferably TiO 2 0.0 - 5 wt.-% zirconium oxide, preferably ZrO 2 based on the weight of said glass flakes. The invention relates also to a method for producing the effect pigments as well as to the use of said effect pigments. The invention further relates to coating formulations based on the effect pigments.