basalt scoria - maroon basalt scoria from Red Hill cinder cone, Inyo County, California - Unit of 5 student specimens

Cinder cone volcanos are made of loose blocks and fragments of basalt that have been ejected from the vent. These form a steep-sided symmetrical cone of pyroclastic ejecta. The ejected lava cools as it flies through the air, and is frequently streamlined to form ribbons and almond-shaped bombs. These, along with pieces of scoria and ejecta of practically any imaginable shape, are commonly termed cinder, forming a cone of loose material that is a challenge to climb. It's two steps up as you slide one step back. Once, while climbing this cone and using both hands and feet, I came nose to nose with a snake who was as surprised as I was. It turned out to be an unusual subspecies of gopher snake and was fairly mellow, allowing a close examination in hand.

Scoria is the silica-poor equivalent of pumice, though the large size of the vesicles and its iron-rich basaltic composition make it unlikely to float, except momentarily.