1.   A cyanide solution is used in mining to separate gold ore from surrounding rock.

2.   A cyanide solution is used to separate gold ore from surrounding rock.

3.   At the mine, a cyanide solution is used to separate gold ore from surrounding rock.

4.   Cyanide is used to separate gold ore from the surrounding rock.

5.   The tailings are left behind after ore has been separated.

6.   Tailings are the residue left after copper ore has been separated.