Mithril ore, like all other mined rocks, respawns at a rate directly proportional to the number of people in the rock's RuneScapeworld. If the world is empty, the ore respawns in 4 minutes; if it is full (with 2000 players), it respawns in 2 minutes. Thus the respawn rate of mithril ore is
where x is the number of players in the world
A table of respawn rates is given below.
A common way to overcome the slow respawn rate of mithril ore is world switching.
This is done by mining the ore on a world until you have mined all the rocks and then logging out to the lobby and switching to a different world. Repeat until the player's inventory is full.
When RuneScape was first released, smelting mithril bars required level 55 Smithing. Jagex later redefined the smithing table such that smelting mithril bars only required level 50 Smithing. This may have been because although mithril requires 55 mining to mine, getting 55 mining is much easier than getting 55 smithing, and as such it would make sense that the requirement to smith it was lower.
The metal Mithril features in many fantasy worlds, sometimes spelled mithral. It is found in both the novel and film series The Lord of the Rings, where it is white, as well as Dungeons and Dragons, Final Fantasy, The Elder Scrolls IV: Oblivion and World of Warcraft.