Moss agate is what’s known as a semi-precious gemstone. It’s formed from silicon dioxide and is a form of chalcedony, which includes minerals that are green in color embedded in the stone.
Despite its name, moss agate doesn’t actually contain any organic matter. In fact, it’s usually formed from volcanic rocks that have been weathered.
Please note: Every moss agate stone has slightly different inclusions in them and yours may not appear 100% identical to the cubes photographed, but will be very similar and very cool looking :)