Jasper

Jasper is an opaque, cryptocrystalline variety of quartz, classified within the chalcedony group but distinguished by its granular structure and heavy load of impurities — up to 20% clay, hematite, or other minerals mixed into the silica. Its name derives from the Greek "iaspis," meaning "spotted stone," a fitting description for a material almost never uniform in color. Reds and browns dominate, caused by iron(III) oxide inclusions, but jasper also occurs in yellow, green, black, and rare blue tones, often banded, brecciated, dendritic, or orbicular. Formation typically involves silica-rich volcanic ash or sediment consolidating over time, sometimes reheated by later volcanic activity, which explains why so many famous deposits sit within ancient ash flows and river gravels.

Typical, widely traded localities include Bruneau Canyon in Owyhee County, Idaho, prized for its fine brown-cream banding within thundereggs, and Biggs Junction and the Deschutes River area of Oregon, source of classic picture jasper with scenic, landscape-like patterning. Morrisonite, from the Owyhee River gorge in Malheur County, Oregon, ranks among the most sought-after picture jaspers for its dense, multicolored patterning. California contributes Poppy jasper from Morgan Hill, its orbicular red "blossoms" set in yellow ground, while Arizona's Cave Creek deposits yield strong reds. Exceptional material also comes from far beyond North America: Mookaite, a silicified radiolarite from the Windalia Radiolarite Formation in Western Australia, shows rich reds, mustards, and creams; Kambaba jasper (an eye-patterned rhyolite) is worked in Madagascar and South Africa; and India supplies abundant red and "Indian blanket" jasper. The single most celebrated particular locality, however, is Madagascar's Analalava district, in the Sofia region near the villages of Marovato and Kabamby, where spherulitic, orbicular material marketed as Ocean Jasper was only discovered in 1999 and remains tightly mined and highly collectible.

Collectors value jasper for the sheer diversity achievable within a single mineral species — bloodstone (heliotrope), a dark green jasper-like chalcedony spotted with red hematite, is a traditional March birthstone; jaspilite pairs jasper with banded hematite in iron-formation rock; and leopard-skin, ribbon, and brecciated jaspers each offer distinct textural collecting niches. With a hardness sufficient to take a fine polish, a specific gravity around 2.5–2.9, and a history of ornamental use stretching back to Minoan seals and Bronze Age tools, jasper bridges lapidary art and mineralogical interest, making regionally documented specimens — labeled by exact locality, from Bruneau to Kabamby — especially desirable to serious collectors.