Chemistry and geologic information for historic ore and ore-related rock samples from mineral deposits in the United States and from archetypal deposits from 27 other countries. Data are provide in Microsoft Access, Microsoft Excel, and CSV formats.

Magnetotelluric data collected in 1989 and 1990 using USGS portable truck mounted systems that measure the distribution of electrical conductivity beneath the surface of the earth. This release provides digital information previously collected, recovered and reformatted for use with modern software. Data are provided in MT/EMAP formats.