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. 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, a stone mold forms in its place. We are offering a 10x13.5x1.25" thick silica/quartz slice that weighs just under 11.5 lbs. This specimen came from Rio Grande do Sul, the southernmost state in Brazil and dates to 180 million years ago. The tree's rings remain clearly visible, and remnants of its bark encircle it. 1.25x2" section at edge has crack, but piece remains intact. One side has been polished for display, the other retains a flat, more natural look.