Great material with large colours variety and textures rare and unique. Most of dinosaur bone comes from the North-American plateau from different geological age. There are various types of fossilizations such as replacement by chalcedony, opal and calcite. Rarely, we find agates with fortifications. Quite often is a mixture of calcite and chalcedony. The higher is the silica content the better is the pattern and so, the value increase. The richest period is Jurassic from the Morrison Formation, along Wyoming, Utah and Colorado. This piece is from Utah, full facet.