Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases,[1][2] is an opaque,[3] impure variety of silica, usually red, yellow, brown or green in color; and rarely blue.

The name means "spotted or speckled stone," and is derived via Old French jaspre (variant of Anglo-Norman jaspe) and Latin iaspidem (nom.

[9] Jasper is known to have been a favorite gem in the ancient world; its name can be traced back in Arabic, Persian, Hebrew, Assyrian, Greek and Latin.

[10] On Minoan Crete, jasper was carved to produce seals circa 1800 BC, as evidenced by archaeological recoveries at the palace of Knossos.

[11] Although the term jasper is now restricted to opaque quartz, the ancient iaspis was a stone of considerable translucency including nephrite.

[15] Terms attributed to various well-defined materials includes the geographic locality where it is found, sometimes quite restricted such as "Bruneau" (a canyon) and "Lahontan" (a lake), rivers and even individual mountains; many are fanciful, such as "forest fire" or "rainbow", while others are descriptive, such as "autumn" or "porcelain".

Jasper is the main component in the silica-rich parts of banded iron formations (BIFs) which indicate low, but present, amounts of dissolved oxygen in the water such as during the Great Oxidation Event or snowball earths.

)[18] Basanite is a deep velvety-black variety of amorphous quartz, of a slightly tougher and finer grain than jasper, and less splintery than hornstone.

It is mentioned and its use described in the writings of Bacchylides about 450 BC, and was also described by Theophrastus in his book On Stones (Ancient Greek title: Περὶ λίθων: Peri Lithon), a century later.

Add to this the fact that many different rock types – having in common the colour black and a fine texture – have, over the ages, been pressed into service as touchstones and it will be seen that there is ample scope for confusion in this petrology- and mineralogy-related field of study.