Lacustrine ironstone with a touch of manganese oxcid is not exploited any more, but in XVIII century it was mined, mostly in the lakes of Karelia. So, the Chernorechensky factories were working in the southern part of Karelian Isthmus, in the river Black, near the village Dibuny, on marsh ironstone, giving nearly 30000 poods of cast iron every year.
Under Peter the Great the Kontshezero iron-smelting factory was working on the local lacurine ironstone. It was built in 1707 45 versts to the north away from Petrozavodsk, on a narrow isthmus between Pertozero and Konchezero. Till 1719 only one copper smeltery was working on the factory, in 1719 – a blastfurnace for smelting cast iron started working too. The copper was being smelt till 1753, the cast iron – till the arrival of the director of Olonetsky mining works of Gaskoin. In his time the factory was rebuilt in 1787, but in 1793 it burnt in conflagration. After being rebuilt it was named Konchezersky iron-smelting factory.
