Dana groupings are a means of classifying minerals by the anion groups that they contain (these are groups such as sulfates, carbonates, phosphates, sulfides, etc.) The listing by Dana groups (http://www.mindat.org/dana.php) allows one to drill down to the subgroups and see which minerals are closely related to them. You can also see the minerals in a Dana group (subgroup) on the mineral display page. They are also accessible in the "Search" button from the navigation header. The Dana groups are named for James Dwight Dana who authored the 1849 book "System of Mineralogy" (there is an 8th edition in English that was published in 1997 "Dana's New Mineralogy").