Stoneleaf

Nestled deep within the wilderness exists a rare forest of rock trees, their trunks awash with ethereal shades of purple and their monstera-inspired leaves an enchanting blue. Unbeknownst to many people, the trees here are live and acidproof, except for a small coalition of elves and dwarves that have formed an alliance.
This unlikely alliance has painstakingly unearthed a method to manipulate the growth of these exceptional trees, masterfully coaxing them to take on forms that can be harvested and later employed in the crafting of weapons and armor. This rare blacksmithing method is capable of forming legendary acid-proof arms, an unmatched defense when it comes to fighting black dragons. The materials harvested from the rock trees are very hard to work with once the they have been separated from the tree, there is a fleeting window where the material is still living and is somewhat pliable if one is nimble enough with a hammer.
In order to bend the trees to their will the Elves consistently sing songs to developmentally shape their growth. It takes an Elf a quarter of his lifetime to grow a single grove of trees. Once the trees are at the perfect stage for harvest, the dwarves use magically enchanted chisels to carefully separate the peice from the tree. Once the peice has been separated it is immediately hammered into its place on weapon or armor, the hardening of it binds it to the material it has been set in. After the dwarves have removed the peice the elves begin a magical song of healing to keep the tree living and producing, the oldest of the trees produce the finest peices.
These unique trees thrive exclusively in regions doused by acid rain. The trees have evolved not to just endure the corrosive downpours, but to also depend on them for growth.