What older movie had people with these jewels in their chest that tell who they can breed with?

The movie you are referring to is "The Time Machine" (1960), based on the novel by H.G. Wells. In this film, the Eloi, a group of people living in the future, have gems or crystals embedded in their chests. These crystals are known as "mate-selecting crystals," and they glow when two compatible individuals are near each other, indicating that they are genetically suited for reproduction.