gold depth, page-12

Pomhat, keep in mind the extra costs to mine and treat big tonnes may be balanced by the greater productivity (tonnes per vertical metre).
In narrow underground mines geology is often your friend, mineralisation may break from the ground, it may have a distinctive colour difference or there may be a rock type which is great for developing in.
You are dead right sloppy work can turn high grade into waste, but then you can do that anywhere