Concoidal fracture is shell-like in appearance. Rocks, like obsidian, which fracture in this manner were highly desirable by our ancestors when making stone tools. If you look at projectile points, for example, you'll see lots of little concoidal fractures all over the surface.
Examples of concoidal fracture:
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| Obsidian: Concoidal Fracture |
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| Chert Flake (debris from making a stone tool): Concoidal Fracture |
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| Obsidian Projectile Point: Concoidal Fractures Used to Shape This Tool |
Cleavage breaks on a flat plan. In other words, the mineral will peal like a sheet of paper or break off like a cube.
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| Cleavage |
Hackly fractures have thin, jagged points.
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| Hackly Fracture |
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