A small shaft sunk from one level to another, as for the purpose of ventilation.

An underground opening similar to a shaft but not starting at the surface. Return to the top of the page. Return to the top of the page. Return to the top of the page. ZONE : An area or region which is distinct from the surrounding rock, either because of a difference in the type of structure or because of mineralisation.

An internal connection between two levels constructed by developing downward.