In contrast to most northern New Jersey quarries, prehnite is uncommon at the Braen quarry, and its distribution is limited to the amygdaloidal
and scoriaceous basalt overlying the pillow basalt complex; it is also found in the openings in diapirs.
It was found in amygdaloidal
cavities in a basaltic dike that intersects the upper sill in the alcove.
basalt flows have amygdale fillings principally of celadonite and silica minerals, with minor amounts of zeolite.
The Las Animas structure has epiclastic sediments overlying an amygdaloidal
andesite on the footwall and epiclastic sediments on the hanging wall.
The top few metres are often amygdaloidal
and mafic pegmatites locally occur with felsic layers ([less than or equal to]2-3 cm).
or Plate) 531, a depiction of toadstone, an amygdaloidal
basalt, from British Mineralogy.
The hole drilled through uniform and amygdaloidal
basalts in the footwall intersecting the mineralized zone consisting of shattered, hematized and brecciated (calcite and quartz fillings) basalts.
Basaltic fragments are abundant in the coarse lithic tuff at Gorhams Bluff where they underlie an amygdaloidal
basalt flow near the top of the section.
Comprising from 10 to 20% of the rock, fragments (1-15 cm in size) include greyish pink aphyric and porphyritic felsic volcanic rocks, dark grey mudstone, greyish green amygdaloidal
mafic volcanic rocks, and rare clasts of massive sulphides.
basalt rock units similar to those hosting lode gold deposits at the Red Lake Mines are being encountered in the current drilling program.
The Long Pond Bay Formation is defined to include a sequence of oxidized, coarsely amygdaloidal
mafic volcanic flows and interbedded arkosic grit on Wood Island, and a succession of hyaloclastic mafic flows, laminated siltstone and turbiditic sandstone exposed on the southeast coast of Grand Manan Island, itself.
Lavas are commonly amygdaloidal
and/or microporphyritic with phenocrysts of feldspar and, more rarely, pyroxene or quartz, set in a glassy to microcrystalline groundmass.