Cummings (1987) has broken down the amygdaloids into four distinct and discernible stratigraphic zones based on the secondary mineralization expected in each.
Quartz, datolite, prehnite and albite are found as pseudomorphs after anhydrite within zones 3 and 4 of the lower and middle amygdaloids.
It is distributed throughout the amygdaloids starting near the bottom of zone 4 and continuing upward into zone 1.
Chalcopyrite is found throughout zones 3 and 4 of the lower and middle amygdaloids as brassy sphenoidal crystals up to 1 cm on datolite, prehnite, albite and heulandite.
Datolite is plentiful in the amygdaloids from the middle of zone 3 downward through zone 4.