Jasper is a semiprecious chalcedony (or microcrystalline quartz), and is usually red, brown or green. Its patterns are much less regular and defined than agate, the other chalcedony variety. Another difference between the two is that jaspers are generally opaque, while agates tend to be translucent (or at least contain translucent bands). This distinction stems from the stones' composition. Jasper contains microscopic "grains" of crystalline quartz and agate has microscopic "fibers" of crystalline quartz. Although the term jasper is often applied to unidentified stones, true jaspers are metamorphic rocks. Learn more about Jasper in the Gemstone Index">
Rhyolite gemstone beads can look very similar to jasper, but rhyolites are igneous rock that is chemically identical to granite. Learn more about Rhyolite in the Gemstone Index.
We've combined the rhyolite and jasper categories, because two popular "jasper" gemstones, rainforest jasper and leopardskin jasper, are actually rhyolite.