The name means "spotted stone", and is derived from Anglo-French jaspre, and from the Greek word iaspis. Jasper is a fine-grained, totally opaque cryptocrystalline form of quartz rock, containing various shades of red, sienna, or green due to mineral impurities such as clay (white), hematite (brownish-red), and goethite (yellow).
Jasper can contain various types of patterns and/or color variations due to the formation process and is categorized as a tectosilicate. These pattern variations are created from the flow patterns in the sediments or volcanic ash saturated with silica which percolates through rock forming the jasper. These flow patterns yield bands, stiations, channels, or eddying swirls in the rock's structure.
The hue or saturation of color can vary dramatically throughout the stone. Some varieties of Jasper have been distorted and/or fractured after formation, subsequently re-bonding into discontinuous patterns due to the filling of these fractures with other minerals or materials. Jasper is commonly associated with interbedded hematite ore deposits from the Precambrian age. Jasper occurs as a petrifying agent in fossil wood (Jasperized Wood) and bone.
The famous European gem cutting and polishing capital of Idar-Oberstein, in western Germany was built on a 500+ year history on mining agate, amethyst, jasper, and quartz found in basalt formations of the Hunsrück Mountains that surround the picturesque Rhineland town.
Jasper crystallizes in the hexagonal / trigonal crystal system, with a cryptocrystalline crystal habit. Jasper is a semi-hard material with a hardness of 6.5 to 7 on the Mohs scale. Jasper is a cryptocrystalline variety of the mineral Quartz (SiO2). Jasper has a refractive index of 1.540. and a specific gravity of 2.7. Jasper's surface luster is vitreous.
Chemical composition: SiO2
Semi-Precious Stones