When picking a starting location, you will be shown what layers of stone are prominent in the area you have selected, and this will give you a clue on what kind of ore to expect, if flux, sand or some other special feature is available.
For more information, see the article on stone layers. (This page is for the stone layers "category".)
This category has the following 9 subcategories, out of 9 total.
Pages in category "Stone Layers"
This category contains only the following page.