Here's a checklist of all of the artifacts in the game.
[ ] Bronze Artifact - Almost immediately after Russell’s first shimmy's across a ledge, the artifact will be in plain sight.
[ ] Silver Artifact - After the first co-op jump there will be a spilt in the road. Take the left path and jump up the rock path (to the right of the vine ledge, which is the right way to go) and the artifact will be on a ledge.
[ ] Gold Artifact - After you knock down the boulder from the left path, follow the right path. Carl knocks a small rock down. The artifact is on the lower drop off in plain sight.
[ ] Bronze Artifact - After pushing a log, there will be a bridge that Carl knocks down. At the end of this bridge is the artifact.
[ ] Silver Artifact - There will be some Snare Traps that you have to bypass. You’ll come to a point where you’ll see 2 Porcupines in a cave. Behind them is the artifact.
[ ] Gold Artifact - There will be an area where you see the house on a cliff. Go forward and there will be 2 mushroom jumps. Make sure that you jump with the [A Button] while on the mushroom to make yourself jump higher and then you’ll be able to reach the artifact.
[ ] Bronze Artifact - In the beginning of the level, after pulling Carl up with Russell, keep going until you see a rock on the left that is a different shade than the rest of the mountain side. Have Carl push the rock and behind here is the artifact.
[ ] Gold Artifact - After a co-op jump there will be a section with lot of flowers on the ground, some wasps, and yellow butterflies. Follow this area to the edge of the cliff where you see a ledge leading to some small jumps downward and a cave leading to the artifact.
** Note: On the way out of the cave you should receive the Excavation Badge (Secret Achievement) **
[ ] Silver Artifact - There will be an area with 3 rocks you need to push and create rising platforms to continue. The artifact is in plain sight. Move all 3 rocks into their locations and one of these will make a platform on the left to get up to the artifact.
[ ] Bronze Artifact - After the Dug hits the button to make the bridge, cross it and you will come across a rock with a different shade. Use Carl move the rock and collect the artifact.
[ ] Silver Artifact - After the dog ambush, use Russell to pull Carl up a ledge. Halfway through there will be a smashable object containing the artifact. This one is actually hidden like that one.
[ ] Gold Artifact - A little further through the level, there will be another swimming section where Dug helps Carl. This swimming second has small waterfall drop offs so you’ll know if you’re in the right area. At the end of the area, there is an electric eel on the right side that you have to get past and behind him is the artifact.
[ ] Silver Artifact - After the dog ambush, the artifact will be at the top end behind some breakable rocks.
[ ] Gold Artifact - There will come a point where Russell needs to cut a vine for Carl to make a co-op jump. Near this area, jump off the mushrooms with the [A Button] jump to reach the artifact.
[ ] Bronze Artifact - After you drop down from pushing a rock you will see a watermelon in your path. To the left of this, in the red butterflies, is the artifact.
[ ] Bronze Artifact – When the level starts, follow the cliff until you see the artifact spinning in the grass.
[ ] Silver Artifact - After you come across a swinging vine jump, follow the cliff around. There will come a point for a vine jump for Carl and, behind the rock, is the artifact.
[ ] Gold Artifact - After getting the Hiking Badge, go all the way right and drop down. You will see the artifact in a small alcove next to a blue mushroom.
[ ] Bronze Artifact - In the first room after Dug moves the boxes for Carl via crank, DO NOT GO UP THE RED FLASHING ELEVATOR. Instead, go towards the screen and smash some boxes to reveal the artifact. Now you can go up the elevator.
[ ] Silver Artifact - After Dug activates the second lift, you will see two paths to take. On the left you will see what looks like plane propellers. Don’t go left yet, as that is the way out. Go right instead and follow it up and around. The artifact will be on your way.
[ ] Gold Artifact - In the room where you find Russell in a cage, on the far right you’ll see several smashable crates. In one of them is the artifact. You might have to fight the camera for this one.