Mama's beads is an artifact that can be found in all three S.T.A.L.K.E.R. games.
"An extremely rare artifact. Keep it safe because it has no negative qualities. Scientists cannot figure out how to create such an object in laboratories." - Shadow of Chernobyl description.
"The thermal nature of Mama's Beads is no longer a secret, but its shape still puzzles scientific minds. The emissions produced by pulses in its thicker sections increase the metabolism of living beings, which helps wounds heal quicker. Emits radiation." - Clear Sky description.
"Much about this artifact remains a complete mystery to scientists. At the same time, it is known for certain that emissions produced by pulses in its thicker sections force blood in open wounds to clot quicker, forming a protective scab. One of the most noticeable effects of this artifact is the increased speed of wound healing. Emits radiation." - Call of Pripyat description.
The structure of the Mama's Beads bears striking resemblance to a DNA's helix structure. In Shadow of Chernobyl, the Mama's Beads artifact was originally created in the Time anomaly. Acquiring the Mama's Beads, which was located at the center of the anomaly, made the anomaly disappear. However, the anomaly was cut from the game.