These crystals can be crafted into High Elven torches. Right-clicking on a grass block while holding one makes Elvengrass, from which Elven portals and giant Mellyrn can be made. If alloyed with iron in a forge it makes a Galvorn ingot. Edhelmir can also be stored in blocks just like ingots can. These are crafted in by putting nine of them in a 3x3 formation on a vanilla crafting table.
The name Edhelmir, such as Gulduril, was invented by the mod team and does not exist in Tolkien's lore. However, the name was created using Sindarin, one Tolkien's elvish languages. The root of the name is Edhel, meaning "Elf". The suffix Mir is also Sindarin, meaning "jewel". When combined, it forms a new word, Edhelmir, standing for "Jewel of the Elves".