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- This article is about the mineral. For other uses see Jasper (disambiguation)
Jasper is an opaque, impure variety of quartz that is usually red, yellow or brown in color. This mineral breaks with a smooth surface, and is often used for ornamentation or as a gemstone. It can be highly polished and is used for vases, seals, and at one time for snuff boxes. When the colors are in stripes or bands, it is called striped or banded jasper. Jaspilite is a banded iron formation rock that often has distinctive bands of jasper. The Egyptian pebble is a brownish-yellow jasper.
Etymology and historical/mythical usage
The name means "spotted stone", and is derived from Anglo-French jaspre, from Old French jaspe, from Latin iaspidem, the accusative of iaspis, from Greek iaspis, via a Semitic language (cf. Hebrew yashepheh, Akkadian yashupu), ultimately from Persian yashp.According to Rebbenu Bachya, the word Yasfeh in the verse Exodus 28:20 means jasper and was the stone on the Ephod representing the tribe of Benjamin.
Types of jasper
Jasper can appear as an opaque rock of various shades of red due to mineral impurities. More usually, jasper exhibits one or more type of pattern or variation from formation processes. Most often, variations rise from flow patterns inherent in the precursor sediment or volcanic ash saturated with silica to form jasper, yielding bands, apparent channels, or eddying swirls in the rock.The hue or saturation of color may vary across the material. Jasper may be permeated by dendritic minerals providing the appearance of vegetative growths. The Jasper may have been fractured and/or distorted after formation, later rebonding into discontinuous patterns or filling with another material. Heat or environmental factors may have created surface rinds (such as varnish) or interior stresses leading to fracturing.
Picture jaspers simultaneously exhibit several of these variations (such as banding, flow patterns, dendrites or color variations) resulting in what appear to be scenes or images in a cut section (as in Biggs, Deschutes, Owyhee, Poppy and other named types). Spherical flow patterns produce a distinctive orbicular appearance (porcelain jaspers such as Blue Mountain, Bruneau and Willow Creek). Complex mixes of impurities produce wild color variations (as in McDermit jasper). Healed fractures produce brecciated jasper (such as Canyon Creek).
See also
"Jasper"