It often gets wider at the source ( deep down) But just as often gets narrower but richer in between.

When it gets near the surface and pressure lessens that the resource widens through cracks in original over burden and gets dispersed and dilluted. That depends on causality of mineral reaching or approaching the surface.

I am essentially a gold bug, so I resort to gold for this example.

Often a gold bearing magma gets near surface, by that I mean within a few kilometers, but it is too deep to be mined or discovered. But water permeates into the depth and dissolves some of the gold bearing minerals. Being deep and under huge pressure the water is super heated and eventually percolates to the surface or near it and turns into steam causing the dissolved minerals to precipitate and concentrate in near surface deposits.
These are reachable and exploitable.

The gold concentrations are often much higher than in the original minerals down below. Water action not only brings it closer to the surface but also concentrated the deposit through precipitation.

That type of action could have happened at Eagle's Nest. ( I refer you to a huge platinum concentration in one of the holes, 70?.) I am just speculating because I have no geological know how nor knowlege specific to Eagle's Nest.

Just throwing ideas on a weekend.