【How-to】What does the slang term jasper mean

Jasper, an aggregate of microgranular quartz and/or chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. … The specific gravity of jasper is typically 2.5 to 2.9.