Some of the most important of basic lavas are the dolerites and basalts.
Some basalts have a glass paste, or "ground-mass," in which the minerals are enclosed.
Many basalts are not columnar, and not a few columnar rocks are not basalts.
Only the hardest rocks, such as granites and basalts, remained.
The lavas and ashes are almost everywhere andesites and basalts, with a little obsidian.
Distinctly developed crystals are also met with in the basalts of Japan, but are usually rare at other localities.
The basalts have spread out in sheets, the surface of which seems to have cooled not long ago.
The principal rocks are andesites, but trachytes and basalts are also common.
Those rocks examined microscopically consist of basalts which are often porphyritic.
In Ireland the basalts attain a thickness of nine hundred feet; in Mull they are about three thousand feet thick.