BRAZIL OPAL IN FELDSPAR

This is a natural untreated slab of opal with feldspar.
Mined in brazil
We have taken a picture of both sides and the stone is wet..
it can be cut as a large specimen or cut into smaller stones.

Feldspar is the name given to a group of minerals distinguished by the presence of alumina and silica in their chemistry.  This group includes aluminum silicates of soda, potassium, or lime. It is the single most abundant mineral group on Earth.  They account for an estimated 60% of exposed rocks, as well as soils, clays, and other unconsolidated sediments, and are principal components in rock classification schemes. The minerals included in this group are the orthoclase, microcline and plagioclase feldspars.