These are whole Black Obsidian rocks. Obsidian is very clean with little to no flaws. Obsidian does not need heat treatment and are ready for spalling. A good choice for intermediate or expert knappers. Please note, we can not see inside our rocks. If you recieve a rock of poor quality with cracks or bad spots, please contact us for replacement solutions. Stone shown in the picture is an example of what to expect. Actual pieces may very. Skill Range: Intermediate to Expert.