Jasper is an opaque, impure variety of quartz that is usually red, yellow or brown in colour. It is composed mostly of chalcedony, microcrystalline quartz, in association with other minerals, which give it colorful bands and patterns. Jasper is often named according to its pattern: landscape jaspers, the most popular, offer a small worldscape in stone. Ribbon jasper, picture jasper, and orbicular jasper describe other designs. 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 Egyptial pebble is a brownish-yellow jasper.
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. 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.
Jasper was a favorite gem in the ancient world, and the name jasper, which means "spotted stone", can be traced back in Hebrew, Assyrian, Persian, Greek, and Latin. Jasper has been used as gemstones and other ornamental objects for thousands of years. In medieval times jasper was said to give the wearer, with God's help, the power to heal insanity and to heal those possessed by devils. In the fourth century, the wearing of green jasper was said to bring rain and to cure snake bites. Jasper amulets were engraved with passages from the Book of the Dead by the ancient Egyptians to procure safe passage for the deceased in the realm of the dead.
Some of the earliest primitive stone tools (axes) fashioned by man's ancestors 2.5 million years ago in the Omo valley in Ethiopia, were made of quartz varieties such as jasper or chert. These materials were used because of their hardness and their isotropic brittleness which made it possible to shape the tools with relative ease.
Jasper is found in many countries. The most notable occurrences include India, China, Mongolia, USA and Czech Republic. In Russia, jasper is found in Ural Mountains, especially around Orsk. Jasper is best characterized by its occurrence, hardness, fracture, density, refractive index and luster.
Characteristics:
Chemistry: SiO2
Class: tectosilicate
Hardness (Mohs scale): 6 – 7
Density: 2.58 – 2.91
Refractive index: 1.54 – 1.55
Dispersion: none
Crystal system: hexagonal
Crystal habit: massive microgranular quartz
Fracture: conchoidal
Transparency: translucent to opaque
Luster: dull vitreous to greasy
