Polychrome jasper is also frequently called desert jasper or royal savannah jasper. Some people might also consider it a variety of "picture jasper".
Where Is Polychrome Jasper Found?
Polychrome jasper is exclusively found in the coastal deserts of Northern Madagascar. It's reportedly found in at least two other locations within close proximity, where it was naturally deposited as rounded, massive boulders, some of which can be quite large.
What Is Jasper?
Jasper is a fairly generic term for any type of opaque, aggregate of microgranular quartz or chalcedony that is colored by mineral inclusions. Jaspers can be found in a variety of colors from red, to yellow, to blue, to green and are typically multi-colored. The most common jasper patterns include interesting marbling and veining, orbital rings, streaks, spots, flaming and banding. There are many different trade names and classifications for jasper (such as Polychrome jasper) many of which have very loose definitions.
How Is Jasper Different Than Agate?
The main difference between Jasper and Agate lies in the amount of impurities in the silica. In jasper there are more impurities causing it to be more opaque and light not to pass through it, while agates have less impurities and will allow for translucence.
How Does Jasper Form?
While agate typically forms within cavities in igneous rock or limestones, jasper often forms when fine particles of sediment or ash are cemented by silica. These particles are what gives jasper its color and opacity. The cementation process is sometimes so aggressive that the sediment, ash or volcanic particles are dissolved or recrystallized into microcrystalline quartz.