Altered Basalt

Nice looking smectite in altered basalts found in western Oregon! As it turns out, too much clay in basaltic rocks makes them troublesome for engineering uses. Take highway road beds and gravel roads for example. Spread this clay-rich basalt on a road and after a few rainstorms you have a muddy mess. Not what the doctor ordered! So while the clays are pretty under the microscope, they can be a royal pain in the bedonkadonk when they get into our roads and buildings. Some rocks should never be used for roads or buildings. That nice porous basaltic sandstone image actually comes from a building built in the 1800's that is falling apart at the seams. Wonder why? The sandstone is not cemented by anything other than a little expandable smectite clay. The building gets wet, the clay expands; the building dries, the clays shrink. A few years later, the building falls apart. Hmmmm. Next time use granite!