The United States Geological Survey (USGS) collected a total of 179 samples of surficial sediment from abandoned mine wastepiles, ephemeral channels, nearby outcrops, and background areas representative of the undisturbed lithology within the Silver Island and Crater Island mining districts (Krahulec, 2018).The samples were sieved to obtain the less than 177 micron fraction. Geochemical analyses were completed through a third-party contract by SGS Laboratories. Samples were analyzed for 49 major, minor, and trace elements using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) methods (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Hf, In, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, U, V, W, Y, Yb, Zn, Zr).