Amygdaloial Basalt - What's in a vug?

Last weekend I made a second trip to McKay Head, near Parrsboro, Nova Scotia. The basalt cliffs here were formed at the Triassic-Jurassic boundary, about 200 million years ago, when the supercontinent Pangaea started splitting into the current day continents. At first glance, the cliffs don’t appear to be too exciting, but this is amygdaloidal basalt which is full of vugs.







At this location, the vugs are filled with thin walled geodes and solid nodules. The outer layer tends to be a blue chalcedony filled with outward radiating opaque quartz crystals that locals refer to as “quartz flowers”. In many instances, the opaque quartz has been coated with geyser opal which builds up thin laminations of quartz over the original crystal. These vugs were just out of reach and beneath an brittle cliff overhang that wasn’t safe to chip at. Chances are, they will be on the beach soon as the cliffs are continually eroding.







I dug through the fresh rock fall at the base of the cliff to find a few samples that fell from this area of the cliffs. There is a blue chalcedony rind with either opaque quartz crystals or geyser opal over quartz crystals.







I’ll post a few more finds in the Specimen section.

Darryl.