Rock Identifier
Red-and-gray jasper (likely orbicular or brecciated jasper) (Jasper, microcrystalline quartz (SiO₂) with iron-oxide pigments) — mineral
mineral

Red-and-gray jasper (likely orbicular or brecciated jasper)

Jasper, microcrystalline quartz (SiO₂) with iron-oxide pigments

AI-generated identification · may be incorrect

Typically opaque, fine-grained, and waxy to dull; red areas reflect hematite/goethite, while gray-blue portions may contain silica and minor volcanic minerals. Hardness is about 6.5–7 Mohs, with no visible cleavage and conchoidal fracture; specific gravity is roughly 2.5–2.7.

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Physical properties

Typically opaque, fine-grained, and waxy to dull; red areas reflect hematite/goethite, while gray-blue portions may contain silica and minor volcanic minerals. Hardness is about 6.5–7 Mohs, with no visible cleavage and conchoidal fracture; specific gravity is roughly 2.5–2.7.

Formation & geological history

Forms when silica-rich groundwater replaces or cements volcanic ash, breccia, or other sediment, with iron oxides producing red coloration. Deposits range from Precambrian to relatively young volcanic settings.

Uses & applications

Used as ornamental stone, cabochons, beads, carvings, and tumbled stones; occasionally used for decorative facing and small lapidary objects.

Geological facts

Jasper is a variety of chalcedony or microcrystalline quartz rather than a single mineral species. The specimen appears naturally weathered or partially polished, and the adjacent reddish material may be bark or unrelated debris.

Field identification & locations

Identify it by its opacity, very fine texture, red iron staining, and resistance to scratching by a steel blade; quartz crystal faces are absent. Common sources include volcanic regions of the western United States, Mexico, Madagascar, Brazil, and Australia.