Jasper is an opaque to slightly translucent variety of microcrystalline quartz, distinguished within the broader chalcedony family by its opacity, its high mineral-impurity content and its frequently dramatic patterning. Jasper is one of the oldest gem materials in human use, having been carved into beads, amulets and seals from Neolithic times across the ancient Near East, Egypt and the wider Mediterranean.

Composition and Structure

Jasper is, like all chalcedony, composed of silicon dioxide (SiO2) in microcrystalline form, with crystallites typically in the micrometre size range. What distinguishes jasper from the more translucent chalcedony and agate varieties is the presence of significant non-silica impurities, typically clay minerals, iron oxides and various other admixtures, which both colour the material and give it its characteristic opacity. Jasper hardness is consistent with that of quartz at 7 on the Mohs scale, with specific gravity of 2.58 to 2.91 depending on impurity content and a refractive index of 1.54.

Colour and Pattern

Jasper occurs in essentially every colour represented in the warm half of the spectrum and in many cool colours as well. The colouring agents include iron in its various oxidation states (red and yellow from ferric oxide, green from ferrous compounds), manganese (brown to black), and various clay-mineral mixtures. Jasper typically shows colour in solid blocks, swirls, bands or mottled patterns, and patterning is often the principal aesthetic and commercial criterion. Many regional jasper varieties have established trade names based on appearance and source.

Named Varieties

Picture jasper, named for its strong landscape-like banding and inclusions, is found in several deposits worldwide and includes Bruneau jasper from Idaho, Owyhee picture jasper, and Biggs picture jasper from Oregon. Ocean jasper, with its characteristic orbicular spherical patterning, comes from a single deposit on the north-west coast of Madagascar and was first described in 1955. Mookaite, with its red, purple, yellow and white banding, comes from the Mooka Creek area of Western Australia. Royal Imperial jasper from Mexico shows distinctive orbicular patterning in pastel tones. Bumblebee jasper, despite its trade name, is properly an iron-oxide-stained sedimentary rock from Indonesia and is not a true silicate jasper. Leopard jasper shows dark spots on a tan or red ground and is sourced from Mexico. Rainforest jasper from Australia and Dalmatian jasper from Mexico complete the most-traded varieties.

Bloodstone (Heliotrope)

Bloodstone, sometimes called heliotrope, is a green jasper or chalcedony with bright red spots of iron oxide. It has been used historically across the Mediterranean and Indian traditions, including for early Christian carving where the red spots were interpreted as the blood of Christ. Bloodstone is one of the alternative birthstones for March in modern lists.

Distinction from Chalcedony and Agate

The boundary between jasper, chalcedony and agate is one of degree rather than mineralogy, since all three are microcrystalline silicon dioxide. The trade convention distinguishes jasper as opaque, agate as translucent with banding, and chalcedony as semi-translucent without banding. Mixed materials such as jaspagate and jasper-agate are encountered where opaque jasper bands alternate with translucent agate bands, and these are common particularly from Brazilian and Idaho sources.

Working and Use

Jasper takes a high polish and has been carved and lapidary-worked since prehistory. Common modern uses include cabochons, beads, decorative inlay, intaglio and cameo carving, and as material for ornamental boxes and small sculpture. The material is favoured for cabochon and bead work because of its toughness and resistance to chipping, and its strong patterning in many varieties means that selected specimens can read as miniature landscape paintings. Higher-grade picture jasper specimens command significant prices for their patterns alone.

Historical Significance

Jasper has been worked since the Neolithic period and is among the most widely distributed of ancient gem materials, with archaeological recoveries from Mesopotamia, Egypt, the Aegean and the Indus Valley. Egyptian scarab amulets in red jasper are particularly numerous, and jasper appears in biblical references as one of the stones of the high priest's breastplate. The Greek and Roman traditions used jasper extensively in carving, and the medieval Latin word for the stone passed into the modern European languages largely unchanged.

Modern Trade

Jasper today is principally sold as cabochons, beads and ornamental specimens, with prices varying widely by varietal name, pattern quality and origin. Ocean jasper from Madagascar and the higher-grade picture jaspers from the American west command the strongest premiums in the cabochon trade. Some material sold as jasper, particularly under fanciful trade names, may be other rocks or composites, and care is needed in disclosure for commercial purposes.