The USGS Geoscience Data Catalog provides metadata for USGS publications and other forms of data release mostly from the USGS Minerals Program. Metadata are data about data. This catalog provides geospatial metadata, information about geospatial data such as images of the earth, maps and the geographical features that maps represent. Geospatial metadata are structured in a consistent way so that once you get used to the format, like cards in a library catalog, it becomes easy to find out what you need to know. This collection is populated via harvest of FGDC XML from a sitemap at http://geo-nsdi.er.usgs.gov/sitemap.xml.