From Dragon Eye Atlas
The Sumegaidau mine mainly produces iron and copper ore, but has a side-branch that runs into rock salt and a single deep shaft that used to follow a small mithril vein, but was lost when excavation work hit an underground aquifier that flooded the entire mine in 81 BV, drowning almost a thousand miners. Three years later, a sidewards release tunnel was completed that emptied the aquifier's stream into what is now the Gleyre river. The mine re-opened one year later and has been running ever since, though the lower levels are now permanently flooded.
The mine is estimated to be about 250m deep from its entrance, with most portions below 200m permanently flooded today.
Sumegaidau mine is one of the richest human mines of Auseka. While it cannot compete with dwarven mines, it employs a good portion of the population around and its ores are shipped to most of Vericum.