This is a piece of a malachite stalactite from the Democratic Republic of the Congo. It has a layer of botryoidal chrysocolla coatingthe outside of it. The malachite sections of this piece display a beautiful chatoyancy that you can see in this Instagram video (https://www.instagram.com/p/CVI3ey4LQLc/)
This piece is approximately 7 x 4.8 x 4.5 cm
