Jasper, a form of chalcedony, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. This mineral breaks with a smooth surface, and is used for ornamentation or as a gemstone. It can be highly polished and 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 inclusions. The specific gravity of jasper is typically 2.5 to 2.9. Jasper is, along with Heliotrope (bloodstone), one of the traditional birthstones for March.

The name means "spotted or speckled stone", and is derived via Old French jaspre


Green jasper was used to make bow drills in Mehrgarh between 4th-5th millennium BC. 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. On Minoan Crete within present day Greece jasper was carved to produce seals circa 1800 BC, as evidenced by archaeological recoveries at the palace of Knossos.

 

For more information try these links:

http://stoneplus.cst.cmich.edu/jasper.htm

http://www.gemselect.com/gem-info/jasper/jasper-info.php

http://www.mindat.org/min-2082.html

http://www.minerals.net/mineral/jasper.aspx