Jasper is an opaque form of chalcedony. It is an impure variety of silica, usually red, yellow, brown or green color. Jasper is rarely blue. Jasper breaks with a smooth surface and is used as a gemstone. It can be highly polished and used for making vases and seals.

When the colors are in stripes or bands, it is called striped or banded jasper. Jaspilite is a banded iron formation rock that often has distinctive bands of jasper. One of the traditional birthstones for March is jasper. The name jasper means “spotted or speckled stone”, and is derived via Old French jaspre.

Jasper is known to have been a favorite gem in the ancient world. On Minoan Crete, jasper was carved to produce seals in 1800 BC. The term jasper is now restricted to opaque quartz. The ancient jasper was a stone of considerable translucency. The jasper of antiquity was in many cases distinctly green, for it is often compared with the emerald.

The original materials are often fractured or distorted, after deposition, into myriad beautiful patterns which are to be later filled with other colorful minerals. Weathering, with time, will create intensely colored superficial rinds.
The classification and naming of jasper presents a challenge. Names includes the geographic locality where it is found, rivers,lakes and mountains. Many are fanciful such as “Forest Fire” or “Rainbow”, “Autumn”, “Porcelain” or “Dalmatian”. A few are designated by the country of origin such as a Brown Egyptian or Red African.

The black flinty jasper found in several New England states of the USA is known as the Lydian stone. It is used as a touchstone in testing the purity of precious metals.