CURRENTLY VIEWING: Jasper
 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.
Jasper can appear as an opaque rock of almost any color 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 mud or 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 dentritic 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 (jasper, agate or dissimilar). Heat or environmental factors may have crated rinds (such as varnish) or interior stresses leading to cracking.
Picture jaspers simultaneously exhibit several of these variations (such as banding, flow patterns, dentrites 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 conglomerate jasper (such as Canyon Creek).
|
|
