What is Jasper? Jasper is an opaque variety of Chalcedony , and is usually associated with brown, yellow , or reddish colours, but may be used to describe other opaque colours of Chalcedony such as dark or mottled green, orange, and black. Jasper is almost always multicoloured, with unique colour patterns and habits. 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 colour; and