Complex sentence: All the ore produced by the mine came from the Greenside Vein, a mineral vein which filled a geological fault running in a north-south direction under the east ridge of Green Side, a mountain in the Helvellyn range, near the head of Ullswater.
Split into simpler sentences: All the ore produced by the mine came from the Greenside Vein, a mineral vein which filled a geological fault running in a north-south direction under the east ridge of Green Side. This is a mountain in the Helvellyn range, near the head of Ullswater.