Harnoff Splitrock  

This mob spawns at +725, +189, -64.22 in the mines. Findable (via Ctrl-F): Yes

You say, 'Hail, Harnoff Splitrock'

Harnoff Splitrock says, 'Greetins to ya friend Human! I've got some of the finest quality steel ores in all the lands! It's a bit troublesome ta keep a large enough supply of it though, it bein sought after by every smith ya know. If you're needin some cash or ore how bout you [an errand] fer me?'

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He gives a quest to refill his stock of High Quality Ore.

His initial stock includes in limited quantities:
75 Block of High Quality Ore
50 Block of Refined High Quality Ore
150 Large Brick of High Quality Ore
100 Large Brick of Refined High Quality Ore
300 Small Brick of High Quality Ore
200 Small Brick of Refined High Quality Ore