Some pieces of Chelyabinsk display an even more unusual type of structure. These rarer meteorites are Impact Melt Breccia stones. Impact Melt Breccia meteorites are very recognizable by the dark gray zones of glassy melted rock which has been injected into spaces and cracks. The dark melt areas have metal in the form of tiny blebs rather than larger metal grains. Small inclusions of the bronze colored mineral troilte are also seen in the dark melted regions of the stone.