Jasper is a rarer variety of chalcedony, therefore one of the silica polymorphs. It is very similar to chalcedony (agate), but chalcedony is fibrous and jasper is granular. It has good acceptance in the ornamental and collection stone market.

Geologically the term has been used in relation to impure chalcedony or microcrystalline chert, which are rocks that are macroscopically opaque and slightly translucent, usually red or brown, may have other colors (yellow, etc.). The colors are due to fine inclusions of hematite, Fe hydroxides and other minerals. The association with banded iron formations (BIFs) is typical.

In the market of collection minerals the term is also used for other lapidary materials, including igneous and sedimentary rocks.

The nomenclature is very confusing, with names derived from appearance (habit) and other names derived from origin, for example. Some names:

Agate jasper, Egyptian jasper, banded jasper, basanite, image jasper, hornstein, Kellerwaldachat jasper, landscape jasper, mookaite, ocean jasper, porcelain jasper, prasem, plasma, flint, zebra jasper, blood jasper, Bird’s Eye jasper, Irminite, dallasite , chrysojasper.

In antiquity, jasper was a highly valued decorative stone among the Greeks and Romans, for example. It was later superseded by other rocks and minerals. Today, pots, vases, table tops and mosaics are still being made and jasper is used in architectural works.

Well known is the jasper found in Sicily, in the region of the city of Giuliana. It has been known since the twelfth century, but had its heyday in the sixteenth and seventeenth centuries. It is found in concretions and fragments in crops in the region. As of 1996, this material was “rediscovered” and today it is very well accepted among collectors. Get local names:

            “Diaspro giallo retato di calcedonio”     = yellow jasper gap cemented by light blue chalcedony

            “Diaspro fiorito reticellato” = dark red jasper breccia with chalcedony light blue with white edges.

            “Diaspro verde e giallo rigato” = jasper zebra in green and yellow.

            “Black Diaspro” = red-black jasper.