Yttrium, cerium, neodymium, lanthanum, as well as trace to minor amounts of other REEs, are present in their structure.

Agardite minerals are a member of the mixite structure group, which has the general chemical formula Cu2+6A(TO4)3(OH)6·3H2O, where A is a REE, Al, Ca, Pb, or Bi, and T is P or As.

[16] Agardite-(Y) from the Bou Skour mine in Djebel Sarhro, Morocco was the first of the agardite-group minerals to be characterized.

[17] It was described by Dietrich in 1969 and was named after Jules Agard, a French geologist at the Bureau de Recherches Géologiques et Minières, Orléans, France.

[18] Agardite-group minerals have subsequently been found in Germany,[19] Czech Republic,[20] Greece,[21] Italy,[22] Japan,[23] Namibia,[24] Poland,[25] Spain,[26] Switzerland,[27] the United Kingdom,[28] and the United States.