African Petrified Wood Agate 6-7mm Table Cut Cube Bead - 15-16 Inch R0861 but can be distinguished by

but can be distinguished by its structure and its lower relative hardness

siderophyllite

with occasional inclusions of Black Tourmaline that crisscross the stone in fibrous patterns

Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks

with every gradient of gray in between

African Petrified Wood Agate 6-7mm Table Cut Cube Bead - 15-16 Inch R0861 but can be distinguished byPetrified Wood Agate is formed from the petrifaction process of primeval trees over the course of many years. Petrification occurs when the wood is covered by sedimentary rock, as waters loosen and decompose the organic elements and replace them with silicate substances, while maintaining the wood's original structure. Preservation is enabled by a lack of oxygen.