Mined materials (4)
I believe the answer is:
ores
'mined materials' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ores that I've seen before include "Rocks or minerals containing metals" , "Metal-bearing minerals" , "Mined minerals" , "Sources of metal" , "Bauxite, haematite etc" .)