Jaspers

Jasper is an opaque, impure variety of quartz that is normally red, yellow and brown in color. This mineral breaks with a smooth surface, and is often used mainly for ornamentation or as a gemstone. It could be highly polished and is used for vases, seals, and at one time for snuff boxes. When the colors are in stripes and bands, it is known as striped or banded jasper. Jaspilite is banded iron formation rocks that are often has distinctive bands of jasper. The Egyptian pebble is brownish-yellow jasper.

Types of jasper

Jasper could appear as an opaque rock of various shades of red due to the mineral impurities. More usually, jasper exhibits one and more type of pattern or even variation from formation processes. Most often, variations rise from flow patterns inherent in the precursor sediment and volcanic ash saturated with silica to form jasper, yielding bands, apparent channels, and even eddying swirls in the rock.

The hue and saturation of color could vary across the material. Jasper can be permeated by dendrite minerals providing the appearance of vegetative growths. The Jasper could have been fractured and/or distorted after formation, later rebounding into the discontinuous patterns and filling with another material. Heat or environmental factors can 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 and its 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 the distinctive orbicular appearance (porcelain jaspers such as normal Blue Mountain, Bureau and Willow Creek). Complex mixes of impurities produce wild color variations (as in McDermott jasper). Healed fractures produce brecciate jasper (such as Canyon Creek