and which one is imitation…

OK, a slightly misleading pair of stones and a bit of a trick question because the natural one on the left has been coated with resin which has altered the lustre of the stone. Malachite is known as having a silky or dull vitreous lustre but the resin has given it a vitreous lustre (sorry about that!). The stone on the right is an imitation – when you look closely with a loupe you can see that the colour banding doesn’t look natural and there are flecks within the layers.

One test that can be done to determine whether the malachite stone you are looking at is natural or an imitation is to do a streak test… this involves drawing the stone across an unglazed ceramic plate to see what colour streak the stone leaves behind. Malachite will leave a green streak, the stone on the right leaves a black streak BUT don’t forget this is a destructive test and you will be removing part of the stone… not to be done anywhere on the stone where it can be seen...