Apparently this whole area was a giant lakebed, millions of years ago. It had layers of silica in it’s bottom. When the Lava flows began crossing Eastern Oregon, they flowed across this huge lakebed, cooking and pushing the silica layers into folds and seams as it went. As more flows covered the preceding lava flows and this old lakebed, these folds and layers of silica became silicified and turned into jaspers agate and common opal. These seams and deposits are in between the lava flows. Many times they can be found by looking for green growth in a line across a barren hillside. This usually indicates a water source seeping from between the lava flows. This appears to be where the opal/agate and jasper is found.