Jasper

an impure variety of minutely crystalline quartz (SiO2). It is usually red, brown or yellow, and some varieties are banded, e.g. Egyptian or ribbon jasper.

Taken from Dictionary of Science

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Jasper, a form of chalcedony , is an opaque, impure variety of silica, usually red, yellow, brown or green in color. Blue is rare. This mineral breaks with a smooth surface, and is used for ornamentation or as a gemstone. It can be highly polished and is used for vases, seals, and at one time for snuff boxes. 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. Jasper is basically chert which owes its red color to iron(III) inclusions. The specific gravity of jasper is typically 2.5 to 2.9.

Taken from Wikipedia