Scoria Scoria Scoria is the vesicular ejecta of mafic lavas. Mafic simply means that the lava or magma is rich in iron and magnesium and poor in silica.
Scoria is commonly in the size range of lapilli to bombs and is black, red, or brown in color.
Because basalt, a mafic lava or rock, is the most common type of lava in Hawaii, scoria is a good general term for most Hawaiian tephra. Photo by Steve Mattox, June, 1995.