C.R.S. § 34-43-108: To hold lode - crosscut - tunnel - adit.

Any open cut, crosscut, or tunnel which cuts a lode at the depth of ten feet below the surface shall hold such lode, the same as if a discovery shaft were sunk thereon, or an adit of at least ten feet in along the lode, from the point where the lode may be in any manner discovered, shall be equivalent to a discovery shaft.