Agate on black base (1.6kg)

This open agate geode comes from Brazil. It was formed from a bubble of gas trapped in volcanic lava several tens of millions of years ago. Over time, dissolved silica slowly crystallized inside the cavity, creating a sparkling lining of quartz crystals.
The outer surface retains the rough volcanic texture, while the cut reveals concentric agate bands in dark tones surrounding the crystal core. The piece illustrates the gradual transformation of volcanic rock into crystal through a long and patient geological process.
Displayed on a black base, this natural curiosity is a collector’s mineral typical of a cabinet of curiosities