Scoria is a light-weight, dark-colored, glassy, pyroclastic igneous rock that contains many vesicles (bubblelike cavities). Foamlike scoria, in which the bubbles are very thin shells of solidified basaltic magma, occurs as a product of explosive eruptions (as on Hawaii) and as frothy crusts on some pahoehoe (smooth- or billowy-surfaced) lavas. Other scoria, sometimes called volcanic cinder, resembles clinkers, or cinders from a coal furnace.
The darker color of scoria has made it less useful commercially than pumice. Locally, it has been quarried for road cinders. US Highway 395 through the southern Owens Valley has been surfaces with scoria cinders from Red Hill, a small cinder cone adjacent to the highway.
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