A group of minerals that have an identical crystal structure, where the only difference between them is the elements contained in their crystal structure. A series by definition must have at least two minerals, which are its end members, or anchor members. Minerals in the series can be a combination of both anchor members.
Some mineral series, such as the Spinel series, contain more than two end members. This means there can be several different combinations of intermediary members. In a few complex mineral series, such as Garnet, more than one element may be replaced by another. A mineral series may contain a member with the same name. For example, the Skutterudite series contains three minerals, and the name of one of them is Skutterudite.
For more information, see "The Chemical Properties of Minerals".