[myhands2]

Hello,

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 ?

myhands2

[tamim83]

It could possibly be iron.  Iron oxidizes to form a reddish compound (Fe₂O₃ or rust) when exposed to air.