It sure looks like sliced and polished pieces of a beautiful agate mineral specimen.....but it's ALL glass!! Such amazing work from Bryan, this is the sort of work he truly excelled at. A LOT of work went into this, with the layers of glass being formed in the hot flame, then sliced up when cold, with each slice then being tumbled and polished. Finally, Bryan strung it all together with nice little spacer beads, ready for wearing as is, or incorporated into an even more beautiful necklace. Or just hung somewhere to be gazed in wide wonder at. That's how it has functioned so far since Bryan created it back in the 2005-06 time frame. Don't miss this rare chance at amazingly unique and beautiful glass!!