Minerals crunched by intense pressure near the Earth's core lose much of their ability to conduct infrared light, according to a new study from the Carnegie Institution's Geophysical Laboratory. Since infrared light contributes to the flow of heat, the result challenges some long-held notions about heat transfer in the lower mantle, the layer of molten rock that surrounds the Earth's solid core. The work could aid the study of mantle plumes--large columns of hot upwelling magma believed to produce features such as the Hawaiian Islands and Iceland.