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A Hertzian cone is the cone of force that propagates through a brittle, amorphous or cryptocrystalline solid material from a point of impact, eventually removing a full or partial cone. An example often occurs when a plate-glass window is struck by a small object, such as an airgun projectile. This is the physical principle that explains the form and characteristics of the flakes removed from a core of tool stone during the process of lithic reduction.
Although it might not be agreed by all, natural phenomena which have been grouped with the Hertzian cone phenomena include the crescentic "chatter marks" made on smoothed bedrock by glacial ice dragging along boulders at its base, the numerous crescentic impact marks sometimes seen on pebbles and cobbles, and the shatter cones found at bolide impact sites. James Byous, working independently (at privately funded Dowd Research, Savannah, Georgia USA) has made a protracted study of Hertzian cones. Some of his work may be found via sharing points (e.g. Academia.edu - http://dowdresearch.academia.edu/JamesByous ) or directly at Dowd Research. He had produced a comprehensive glossary on Hertzian fractures and related terms (which may be downloaded from http://www.dowdresearch.org/Hertzian-Glossary.html ).