Created by petroleum geology consultant David Barthelmy, the Mineralogy Database Web site reportedly contains 4,281 individual minerals and descriptions. Visitors can browse the minerals by crystal system, by x-ray powder diffraction properties, by chemical composition, by the Dana system or the Strunz system, by physical and optical properties, alphabetically, and by mineral pictures. The large amount of information available for each specimen is impressive, especially for a personal Web site. Everyone from curious kids and adult hobbyists to academics and researchers will find something worth exploring on this extensive site.