Large half of a CHALCEDON FEUERSTEIN tuber.
The correct name of this quartz variety is CHERT. CHERT is considered the impure form of FIRE STONE
Impurities in HORNSTEIN lead to a variety of colors and textures. The difference between CHERT and FLINT (flint) is small and is referred to as Crypto Crystalline Silicate - CCS.
These stones are simply called jasper in the trade, as is the case with other stones, with some fantasy name - polychrome jasper, imperial jasper or dessert jasper etc.. We have already seen hundreds of tons of different varieties of real jasper as rough stones, but never in nodular form with razor-sharp fracture edges and a weathered rind.
This piece comes from sites in Mahajunga - Madagascar
Weight: 2.2 kilograms Dimensions: 20 x 13 x 10 cm
For hobby grinders: First-class polishing with CEROXYD