Jadeite

An incredibly tough mineral that is typically green, sometimes found at a quality that beautiful gemstones can be made from it. There have been civilizations that made weapons from it, while others used it to carve in messages. Within the valley, it once was one of the key ingredients to creating Ancient Runes. Unfortunately, the material is rare. There are little supplies available for us, and we have yet to find the veins used by the past residents of the valley. Perhaps the veins ran dry, which would explain why it became more and more expensive for them to produce Ancient Runes.
Judging on the variety of Ancient Runes discovered, it seems there were two possible ways to use jadeite for this process. First of, dust would be combined with other ingredients to produce the liquid needed to draw said runes. The other use was as a base to engrave patterns in that were then filled and hardened. Not many runes were found that were made in the second way, but those that were, seem more powerful than the others. This suggests that a Jadeite pillar helps sustain the protective effect of the runes.
Interestingly enough, while runic crystals themselves can be corrupted over time, as a found stash proved, jadeite blocks next to it were still untainted. This has quickly resulted in some folks trying to carry some with them, just in case it helps stave off the Corruption. The Ravenmight Institute is still experimenting and hoping to find ways to reproduce or repairs the wards needed to protect and heal people, so that there is a way back even for those corrupted beyond the point of healing.
Right now, the scholars of the Ravenmight Institute are asking Scouts to keep an eye out for any personal diaries or stories involving miners. They hope that this way, they can find clues on where in the Depths to look for veins.