Petrified wood is the name given to a special type of fossilized remains of land vegetation. It is the result of a tree or tree-like plants having completely transitioned to stone by the process of permineralization, wherein all the organic materials have been replaced w/minerals, while retaining the original structure of the stem tissue. Unlike other types of fossils which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen which inhibits decomposition. Mineral-laden water flowing through the sediment deposits minerals in the plant's cells and a stone mold forms in its place. We are offering a 8-3/8x12.75x5/16" thick silica/quartz slice of wood that came from Rio Grande do Sul, the southernmost state in Brazil and dates to 180 million years ago. The tree's rings remain partially visible, and its bark still encircles it. Both sides have been polished for display. Lovely lavender coloring.