I have a rock (breccia, weight 2 kos.+++).
Many clasts (cemented in a rusty brown matrix) are magnetic. Among them are some with red/orange colour. When scratched with a small sharp knife a shiny metal appears (doesn't look like copper). After some time again (hours?) the metal cannot be seen and the clasts will have regained the red/orange colour all over.
Can anyone tell what metal has those properties ?