In valguero, there is an easy place to get these. In the chalk hills spawn 2 (i think) the place where there is an island surrounded by rocks and a moat of water. If you go up, you will see land above that place, and a lake on the top connected to there. Right underneath the land brige of the lake, you can find lots of crystal and obsidian, all outside on a little hill. No dangers, maybe a few raptors or so (rarely)