Bog-iron-stone is a brown-blackish ferruginous rock. It arises in lump-like depositions about 30 cm under the meadows/grass surface. Those deposits were build in Northern Germany after the last ice age, during the Holocene. This happened primarily in the valley sand areas of the river systems which drain southwards to the Elbe (Elde, Rögnitz, Sude, Schale and Boize).
Since ice age bog-iron-stone was exploited and smelted with an iron concentration of 45 % ferric oxide. In Mecklenburg the iron production out of local lumps is known since 300 before Christ. Because of an absence of wood it ended in the middle of the 18th century. In the 18th/19th century the bog-iron-stone lumps were used as a cheap building material for farm- and dwelling houses, churches and town wall in rockless landscapes like the “Griesen Area”.