Tomb of Khufu (Location)
One of the great pyramids- the one with the fast travel point on top.
You'll come through here during your hunt for the Hyena. Whereas that quest takes you to the very bottom of the pyramid, searching for the tablet should have you looking for all the ways up. Ignore the inviting crack to your right in the first passage, and instead take the twin ramps all the way to the top, where a small square passage can be found.
Enter, loot, and look for a scarab wall.
Push through for a treasure room, but not the final treasure room.
Destroy the two square panels on either side of the far door (they'll be hilighted in pulse-vision as well). Sand will pour out and, when both are broken, the door will lower partway.
Climb through for the real treasure room, and the tablet.
Reading the tablet completes the location
You can fast travel out from here, but exiting through the small square crawl-way at the far end of the room will lead you to more lootables, including some silica.