I'm trying to complete the "still in the dark" quest so I can go and get the BoS power armor and keep the NCR from wanting them dead. I've got the other two holotapes but the one that's supposed to be in the black mountain crater isn't there... the quest marker is telling me to go inside the rock mountain between the canyon and the road to the radio tower area. I can't just console command it in because I'm on xbox, and when I go back to older saves its still not there. I've tried searching the forums, and googling, but no one seems to have a legitimate answer. I'm feeling more neurotic than Muggy right now! Please dear god someone help me! Thank you in advance!

There are two possibilities: Either you're searching the wrong crater, or you're suffering a game glitch. Since you're on an xbox, I cannot help you if its the latter so I will provide information related to the former. You'll know it's the right crater if you're fighting Centaurs & Evolved Centaurs, most notably a named Centaur, Moe.

This is the southern approach to the right crater via Scorpion Gulch.

http://i.imgur.com/UC8hAhI.jpg

This is the crater proper:

http://i.imgur.com/C2CBqnu.jpg

The Paladin corpse:

http://i.imgur.com/4LVDRso.png

World map location:

http://i.imgur.com/LiXdRX3.jpg

That's the crater with all the blasted centaurs and radiation and skeletons in the crater. Which means its a glitch. Dangit.. thanks though!