Jasper
Jasper is a form of chalcedony, an opaque, impure variety of silica.
Common colors found in Jasper are: red, yellow, brown or green. Blue in Jasper is more rare.
Jasper is widely used as a gemstone cabochon and it can be highly polished.
When the colors are in stripes or bands, it is called striped or banded jasper.
The colors of the Jasper stemming from the mineral content of the original sediments or ash.
The patterns seen in Jasper arise during the consolidation process forming flow and dispositional patterns in the original silica rich sediment or volcanic ash.
The jasper was known since the early Biblical days and it was one of the twelve stones in the Jewish High Priest's breastplate, described in Exodus 28.
Jasper often show what is called dendrites. These are inclusions that appear as vegetative growth.
Dendrites are created by the diffusion of minerals along discontinuities in the original material.
The names of the different Jasper specimens has many sources.
They may describe a geographic locality where it was found, a fancy description of what they look like such as "Rain-forest", or any other description such as a season of the year.
Following are several types of Jasper:
Picture Jaspers - has banding from flow or dispositional patterns (from water or wind).
Dendrite - appear to be scenes or images.
Orbicular - caused by diffusion from a center as in Leopard Skin Jasper.
Brecciated (broken) - produced from healed, fragmented rock.