So diamonds are the hardest natural substance, but can be broken/shattered by impacts.
If a planet had a large mountain range made of diamond (maybe the size of the Rocky Mountains on Earth), would it erode at all? (This is the same system in How close to a supernova can a planet retain an atmosphere? so the diamond mountains and general bizarre geology is because this planet started out as an ice giant, got burned down to a "chthonian planet" core, then got new oceans/atmosphere from a bunch of comets).
I'd like this to remain a barren and lifeless (and therefore traditionally feared & avoided) area, because no soil means no plants means no food sources and no real ecosystem, but would it work that way? Would windblown dust from elsewhere cause some soil to accumulate even if the mountains were un-erodable? Would lightning shatter the mountains enough to produce diamond-dust that could erode them further?
Or is the concept of diamond mountains just stupid? If so, is there another way to get a soilless large area? (It needs to cover at least a significant part of a continent and remain soilless/lifeless for thousands of years and preferably tens of thousands, so new volcanic rock won't work.)