Madagascar Dendiritc Green Opal 10mm Round A Grade - 15-16 Inch Magnesite It is an aluminum borosilicate

It is an aluminum borosilicate mixed with iron

according to the Mohs hardness scale

blue or gray

Only a small percentage of Wampum shells have deep layers of purple and are thick enough to make beads

It is one of the most rare and sought after forms of Agate

Madagascar Dendiritc Green Opal 10mm Round A Grade - 15-16 Inch Magnesite It is an aluminum borosilicateThis 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.