Bootjack Cavern is an unmarked location in the Mojave Wasteland that is east of the wrecked Highwayman. From there, head due east (toward Lucky Jim Mine) until you reach the cliff face, then head north along the cliff.
The cavern entrance faces west, towards the road. The Pip-Boy display is deceptive because it displays the quest marker on the east-facing side of the mesa, in the cave's interior. Players having difficulty finding the location would be well-advised to begin at the road and head east, rather than beginning at Lucky Jim Mine and heading west.
The cavern is a small cave consisting of three sections which are populated by fire geckos.
Inside the cave there is a deposit of sulfur and potassium almost identical to the deposit in the Vault 19 sulfur caves, only smaller and not explosive.
Bootjack Cavern appears only in Fallout: New Vegas.