Not an impact breccia: impact melt rock    

Impact melt rock (granophyre), Vredefort impact structure (South Africa).

Although macroscopically very similar to polymictic impact breccias, the term "impact melt breccia" should be avoided. Different from a breccia which by definition has a clastic matrix, an impact melt rock has a matrix solidified from a melt (glassy or crystallized). Also see: http://www.impact-structures.com/melt/impactmeltpage.html