Jasper

The name "jasper" unites the big group of mineral formations of different genesis, but with the similar physicomechanical and art-decorative properties. The jasper consists of quartz (80-90 %) which represents the microcrystalline unit of chalcedony, and also impurity-pigments. Oxides of iron manganese paint jasper in yellow, red, brown, violet, black tone; epidote and chlorite give green color; blue colour gives glaukofan.

All kinds of jaspers can be divided into such groups: actually jasper - rocks of mainly quartz structure micro-and hide- grained structures; jasper-like quartzite and hornfels - rocks which differ from jaspers with micro- and small-grained structure and characteristic mineral impurities; jaspermoids - silicon formations of mainly chalcedonic structure; jasper-like rocks of feldspar-quartz structure.  In each of these groups there are some kinds relative to the texture features.  

The specification

Hardness

from 6,0 to 7,0 on Moos scale

Density

from 2,58 to 2,91

Factor of refraction

from 1,53 to 1,54

Agate deposits

The red jasper is extracted in India and Venezuela; spherical - in California; a striped jasper - in France, in Germany, Russia.