On an atomic level, pyrites want to form cubes, as they're part of the isometric crystal class. This piece, however, is more unusual as it formed in an elongated rectangular prism, reaching over 4cm, instead! This is the rarest form of pyrite from the prolific locality here, seen in one out of 1000 crystals. if that. This piece was cleanly repaired, as nearly all of the pyrites separate from their matrix during mining extraction. Note that with matrix specimens of this material, almost uniformly the matrix is either stabilized, or the crystal repaired back into its natural place of origin (likely, both). From the personal collection of one of the workers and preparators at the mine, who had set back a dozen fine specimens he worked on over the years and sold us the little collection recently.