The chain-shirt given to Bilbo in J.R.R. Tolkien’s The Hobbit is made of mithril. Thorin’s company finds the small mail shirt in the treasure hoard beneath the Lonely Mountain, and Bilbo wears it during the later part of the quest.
Mithril is a fictional metal prized for being exceptionally light, strong, and valuable. Tolkien describes it as originating in Moria, where the Dwarves mined it. Its name combines Sindarin elements associated with “grey” and “glitter,” producing the sense of “grey glitter.”
Bilbo’s mithril shirt later becomes important in The Lord of the Rings. He gives it to Frodo, who wears it during the journey to Mordor. The armor protects Frodo from a fatal blow in Moria and helps save his life during the escape from the Tower of Cirith Ungol.
Mithril should not be confused with real metals or with the Silmarils. The Silmarils are three legendary jewels made by Fëanor, while mithril is a mined metal used for armor, weapons, and other objects.