Cyrtonaias tampicoensis (also known as the Tampico pearly mussel) is a freshwater bivalve mollusc belonging to the family Unionidae.

[8] Cyrtonaias tampicoensis can reach sizes over 130 mm (5.1 in) in length and is similar to Mercenaria or Spisula marine bivalves.

Calling back to the Concho pearl, it exhibits a light pink and lavender hue, this is due to C. tampicoensis having the same coloration in the inner shell.

Having a muscular foot for movement, a calcareous shell, and a lack of head, it lives the life of a typical bivalve.

[8][page needed] It can attach to the substrate via the byssus threads or move around, as the mussel filter feeds for survival.

[5] Even in the present day, the GIA (Gemological Institute of America), recognizes this pearl as a naturally occurring phenomenon, and exclusive to C.

[11] Nine loose pearls were donated from Stone Group Laboratories for study and cataloging, as a natural Concho is hard to find in the present day.