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 ...