Diamond Nodes begin appearing at level 50 in the mines, at approximately 1 in 500 chance of appearing in place of a stone. For every level after level 50, frequency increases by .000016 per level. This makes for a .0028 chance for a diamond node to appear in place of a stone at floor 100 (1.2 in 500 or 7 in 2500), and ultimately a .003104 chance for a diamond node to appear in place of a stone at floor 119 (1.552 in 500 or 194 in 62500).