The work was undertaken to provide a practical, and as far as possible, a complete list of specific gravities of minerals. An accurate specific gravity determination can usually be made quickly, and this information when combined with other physical properties commonly leads to rapid mineral identification. The work should not be regarded as an index of all known minerals, as specific gravities of many minerals are unknown or known only approximately and are omitted from this list. The list, in order of increasing specific gravity, includes all minerals without regard to other physical properties or to chemical composition. The designation I or II after the name indicates that the mineral falls in the classes of minerals described in Dana, System of Mineralogy, 7th ed., volume I or II. Those not so designated are silicates which will appear in volume III (in preparation). Hydrocarbons have been omitted. Determinations of most specific gravities were made on natural materials; a few made on synthetic material are indicated by the letter S after the value. The letter C indicates calculated value. In the case of some isomorphous series and complicated groups such as apatite, amphiboles, pyroxenes, and clay minerals, only well-known members are listed. Specific gravities for varietal names or unnamed minerals are generally omitted.