Madagascar Dendiritc Green Opal 10mm Round A Grade - 15-16 Inch 6-8x12-25mm This stone is relatively soft

This stone is relatively soft

There are 2 specimens pictured to show that there are variations in the size and color

and much of the black Onyx on the market has been artificially colored

Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks

however they are not currently sourced from that particular region

Madagascar Dendiritc Green Opal 10mm Round A Grade - 15-16 Inch 6-8x12-25mm This stone is relatively softThis variety of opal is named "dendritic" for the small inclusions within it that resemble moss or ferns. These inclusions consist of iron, manganese and other metallic oxides captured during the forming of the rock. Opals are hydrated amorphous forms of silica, created when silica hardens within the fissures of other stones.