M125 - Thunder Egg halves.
Good quality, 3" to 5" specimens have been cut in half and polished on the face.
Mostly agate chunks on face; some with small pocket lined with white calcite or druse quartz crystals.
Scientist do not agree on the
processes forming Thunder eggs. Some insist that the characteristic and
unique internal pattern of typical Thunder eggs is due to expansion and
rupture of rock by gasses. Others claim the pattern is due to desiccation
(drying) of a colloid or gell. Some eggs have layering that is fanned
from one edge, because the egg was rotated by earth movement while the
filling was being deposited. This and other features suggest that the
complete development of some eggs may have taken considerable time, and
the filling-in of the egg may have recorded a series of geologic
events. Some eggs contain brecciated rock fragments, while others show
faulting, offset, and healing.
These specimens are from Oregon.
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