During the geological formation gold particles can be encapsulated inside minerals particles such as pyrite, arsenopyrite and some silicate minerals. Try to break the crystal structure and liberate the gold grains is sometimes impossible due to gold size is very tiny (0.1 µm) and comminution equipment is not able to liberate gold. Typically, this problem produces gold losses and the solution can be complex. Perhaps, cyanidation is the main process affected by gold particles occluded and encapsulated inside other minerals.
Encapsulated gold ore