This is a 2.8" wide, polished green opal sphere from Madagascar. This sphere has been polished into a perfect round sphere from a larger chunk of rock. The coloration in this specimen contains primarily vibrant green and sporadic red-brown.
This specimen comes with the pictured display stand.
Green opal is an amorphous variety of quartz, with the chemical composition of SiO2 · nH2O. This hydrated silicate mineraloid has the associated chemical composition and lack of crystal structure that terms this mineral conglomerate as an opal.
During formation, microscopic holes form within the silica, forming secondary silica lamellae-like strings throughout, giving the rock its inner web-like appearance.