Another major goal of this database is to document and define important petrographic and geochemical characteristics for stratigraphic units and for rock alteration. Petrographic analysis provides most powerfully effective data for such rock properties, but analytical accuracy is always an unspoken issue. This database provides unprecedented quality assurance to address analytical accuracy of mineralogical data from confirming or revising microprobe analyses. The database provides these quality assured petrographic data linked with supporting mineralogical data, and with other types of chemical or mineralogical analyses from other splits from the same sample. These relationally linked data provide a unique body of information that can, properly studied, advance the science of petrography.
Available geologic and geochemical information has not been completely added
to the database; a large number of available geophysical logs have not been
added, and some laboratory data originally contained within GEODES has not yet
been added. We plan to continue the addition of such data, and to slightly expand
the type of information within the PGG database. We encourage users to suggest
improvements and to point out published sources of information that could be