Grofle half of a CHALCEDON FEUERSTEIN tuber.
The correct name of this quartz variety is CHERT. CHERT is considered to be the impure form of FEUERSTEINS
Impurities in the HORNSTEIN lead to a variety of colors and textures. The difference between CHERT and FLINT (firestone) is small and is called Crypto Crystalline Silicate – CCS.
These stones are simply referred to in trade, as with other rocks, as jasper, with any fancy names – polychrome jasper, imperial jasper or dessert JASPER etc. We have already seen hundreds of tons of different real jasper varieties as raw stones, but never in tuber shape with knife-sharp broken edges and a weathering bark.
This piece is from sites in Mahajunga – Madagascar
Weight: 2.2 kilograms Dimensions: 20 x 13 x 10 cm
For hobby grinders: First-class polish with CEROXYD