Opalized Wood - Virgin Valley, NVOpalized Wood is a type of petrified wood that is composed of opal rather than chalcedony or other minerals. It almost always consists of common opal, but in rare instances, petrified wood composed of colorful, precious opal is formed. The ancient forests of Virgin Valley, Nevada were covered by volcanic ashfall over 14 million years ago. Over time, dissolved silica moved by abundant groundwater, filled the cavities of woody stumps, limbs & branches