Some minerals and rocks do not demonstrate a parting or cleavage along specific planes but they do have a consistency in how they break, The resulting surfaces are described as conchoidal (obsidian) uneven (hornblende) etc, The important types of fracture are demonstrated with this collection, 6 specimens approximately 1 1/2"" x 1 1/2"" number-coded, American Educational Products have a lead ship time of 21 days, SKU: AMED526