Ann: Intersections of Bonanza High Grade Gold Plus Visible Gold,EVN-ERM.AX, page-23

PeterPlus, the best way to explain this in simplistic laymen terms is as follows.

Imagine the picture of a mushroom. The stem of the mushroom represents the mineralisation that has been discovered by ERM to date. The top of the mushroom represents what is called the supergene enrichment zone. The mineralisation flows up from deep through the stem and then flowers out in a wider zone at the top.......... like a mushroom.

The flowering out is the supergene enrichment zone and usually causes much lower grades, but at much greater area......... and close to surface. These wider zones at lower grades are economical because they are so close to surface and open pit mining is much cheaper than underground mining.

The stem is where the grades are more concentrated and that is what is needed to make underground mining economical.

The above explanation is very very simplistic, but normally helps those learning about mining and associated geometry of the geology to get a basic understanding.

Cheers