Jasper is an opaque variety of silica composed of microgranular quartz and/or cryptocrystalline chalcedony along with other mineral phases. It is characterized as an impure aggregate that typically appears in shades of red, yellow, brown, or green, though it can rarely be found in blue.
The common red coloration in jasper is attributed to the presence of iron(III) inclusions. The mineral has a density typically ranging from 2.5 to 2.9 g/cm3 and breaks with a smooth surface. Due to these physical properties, it can be highly polished and is frequently utilized as a gemstone or for ornamentation in items such as vases, seals, and snuff boxes.
Jasper is also associated with jaspillite, which is a banded-iron-formation rock that often features distinctive bands of the jasper mineral.