Bird's-Eye Coal from Greymouth, New Zealand

Excellent examples of bird's-eye coal from the Tertiary bituminous coal measures of Greymouth, New Zealand, are described. The "eyes" consist of concentric rings, each ring a miniature ridge with slopes directed radially in opposite directions from the crest line of the ridge. They are believed to be the product of conoidal shearing induced in material of suitable physical character by tectonic stresses.