Orbicular jasper is a variety of

jasper Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases,Kostov, R. I. 2010. Review on the mineralogical systematics of jasper and related rocks. – Archaeometry Workshop, 7, 3, 209-213PDF/ref> ...

which contains variably-colored ''orbs'' or spherical inclusions or zones. In highly silicified

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

and

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

crystallize in radial aggregates of needle-like crystals which provide the basis or ''seed'' for the orbicular structure seen in this kind of jasper. The material is quite attractive when polished and is used as an ornamental stone or

gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...

. Various local or commercial names have been used for the material, such as kinradite, oregonite, owyhee jasper, ocean jasper and poppy-patterned jasper, depending on the source. ''Poppy-patterned jasper'' or ''poppy jasper'' is the varietal name for material from several locations, but the most well known is from

Morgan Hill Morgan Hill is a city in Santa Clara County, California, at the southern tip of Silicon Valley, in the San Francisco Bay Area. Morgan Hill is an affluent residential community, the seat of several high-tech companies, and a dining, entertainmen ...

Santa Clara County, California Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259, as of the 2020 United States Census, 2020 census. Santa Clara County and neighboring Sa ...

. The trade name ''ocean jasper'' is used for a variety found along the intertidal shores of northeast

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

. In

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...

orbicular jasper is found in altered rhyolite beds noted for a variety of jaspers and related

agate Agate () is a common rock formation, consisting of chalcedony and quartz as its primary components, with a wide variety of colors. Agates are primarily formed within volcanic and metamorphic rocks. The ornamental use of agate was common in Ancie ...

s. Also orbicular jasper (like Ocean jasper) has been found in a new location in Bulgaria in early 2017 by Nikolaos Dafnis and Asimina Sklari and they gave the trade name Bulgarian "Orbicular Arda Jasper TM"

Gallery

File:Poppyjasper.jpg, Unpolished poppy jasper, Morgan Hill File:Jaspe orbiculaire Madagascar 1597.jpg, Madagascar orbicular jasper (detail) File:Orbicular Jasper from Bulgaria.jpg, Bulgarian Orbicular Arda Jasper TM File:S20200424 0008.jpg, Bulgarian Orbicular Arda Jasper TM Bulgarian "Orbicular Arda jasper TM"

References

External links

R. V. Dietrich - GemrocksAgate variety names - University of Nebraska-Lincoln
{{Silica minerals Jasper Geology of California