Sin-Kamen (Синь-Камень, in Russian literally – Blue Stone, or Blue Rock) is a type of pagan sacred stones, widespread in Russia, in areas historically inhabited by both Eastern Slavic (Russian), and Uralic tribes (Merya, Muroma[1]). Unlike Sledovik (both Sledovik proper and Cup-stones), Blue Stones did not have major hallows on them, and were venerated in a simpler way: by pouring water on them, or leaving food offerings. Some of the Blue Stones are still known, and to some extent venerated by local population.
If used as a personal name, Sin-Kamen (Blue Rock) usually refers to the most famous sacred stone of this kind, located on a shore of Lake Pleshcheyevo near Pereslavl-Zalesskiy. While in the majority of cases, the stones belonging to the Blue Stones type, have a black, or dark gray color, this particular stone does indeed look dark blue, when wet.[2] The stone surface is covered with small knobs;[2] its weight is estimated to be about 12 tons[3]