Distinguishing of jasper might not be easy to those who are nor familiar with it and indeed most of the time jaspers are identified or even sold as agate.
The most important difference between agate and jasper is the degree of clarity. Agates nearly always show some degree of clarity, but jasper is never transparent or even semi-transparent and does not let light pass through.
Jasper is a very abundant gemstone exhibiting surprising variations and is one of the most affordable stones used in jewelry.
Mookaite jasper is one of the most precious varieties, though still affordable.