Jasper is distinguished from the other agate quartzes by its complete opacity, even at its edges; it is regarded as an agate quartz combined with a ferruginous clay, which gives it its peculiar colour, opaqueness and dull appearance. There occur deep red, violet, lavender, ochre, black and green varieties, this latter, when strewn with bright red spots, being known as the blood-red jasper.

By Jasper-onyx is understood a chocolate brown variety, with bands or ribbons of a dull green. Egyptian jasper has a cream or buff ground, varied with veins or zones of a bistre brown, interspersed with black dendritic spots. The striped or banded jasper is an assemblage of all these varieties, often accompanied by chalcedony.