Hellblade: Senua's Sacrifice has a total of 44 collectibles known as lorestones, scattered throughout the 11 chapters of the game.
The game does
NOT have chapter select, or any mode to mop up collectibles. However, progress does carry between playthroughs, so you can grab what you missed on a second playthrough if necessary. This is the only missable achievement in the game, and everything else will be rewarded through natural progression. Your progress can be seen on the outside ring of each stone. Most of the lorestones are easily found, but chapter by chapter timelinks are available below:
Chapter 1 - 0:34
Chapter 2 - 2:16
Chapter 3 - 6:30
Chapter 4 - 8:31
Chapter 5 - 10:15
Chapter 6 - 13:35
Chapter 7 - 17:00
Chapter 8 - 21:31
Chapter 9 - 23:37
Chapter 10 - 23:42
Chapter 11 - 27:11
NOTE: Lorestones are only saved at checkpoints. If you die, you may need to pick up certain lorestones again!
NOTE 2: The game has been updated so that lorestones are unlocked in order, and the symbols are not necessarily tied to the locations. This means that certain lorestones have multiple possible symbols on them based on what you've collected before them. If you miss one in a chapter, try to grab all lorestones for that chapter just in case.