Figure 1
From: Estimating the capacity for production of formamide by radioactive minerals on the prebiotic Earth

Factors causing heterogeneous distribution of energy from radioactive placer minerals. (a) Global distribution of major modern heavy mineral placer deposits. (b) Concentration of heavy mineral grains (dark layers) within a typical beach placer deposit; image courtesy C. Bern, United States Geological Survey. (c) Spatial distribution of α, β and γ particles around a single radioactive mineral grain.