Basalt tuff/scoria
Basalt tuff scoria

Basalt tuff/scoria

Extrusive igneous rock of mafic composition
Original rock was volcanic origin associated with Miocene or older volcanic ranges along the California/Arizona border region. Fragment of dark lava-rock are embedded in a lighter colored frothy scoria matrix.
River cobble from Colorado River terrace near Blythe, CA.
https://gotbooks.miracosta.edu/rocks/igneous/4.html 2/2/2021