The Heart of the Oasis is an artifact that can be found only in S.T.A.L.K.E.R.: Call of Pripyat from the centre of the legendary Oasis.
"Apparently, it is a crystallized plant, which took over the inherent properties of the Oasis. Its effect on this organism can only be described as extremely beneficial, however, unlike the Oasis itself, the artifact is extremely radioactive." - The Heart of the Oasis artifact Call of Pripyat item description.
Artifact "Heart of Oasis" is a crystallized plant. The name of the artifact is due to a comparison with the source, which has a beneficial effect on the entire human body as a whole. Artifact "Soul" ("Clear Sky", "Call of Pripyat") has grown into anomalous vegetation, forming around itself an anomaly "Oasis".