This heavily patinated chert flake is from Germany.  The surfaces of the flake have significantly altered since the flake was made and discarded.  It may date to the Pleistocene.

 

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The surfaces of this chert flake have devitrified over time as the surfaces crystallised.  The edges of the devitrified stone have crumbled away in some areas.  This indicates considerable age, although stone can patinate relatively rapidly under certain conditions and depending on the nature of the material.  Flint and chert devitrifies more slowly than metamorphic and volcanic rocks, and it is possible that this artefact dates to the Pleistocene.

See the annotations for technological details about this stone tool.