Tiers

From Official Runecraft Wiki

Most vanilla Minecraft blocks may be used in the construction of runes. Each block has been assigned a tier value based on their rarity and difficulty to obtain, which affects the potency of the rune.

Consult tier block for a partial list of tiered materials.

Note: Server admins may change which tier a material is as of runecraft 2.11. See disabled-runes.txt for details.