Mercenaria mercenaria has a large, heavy shell that ranges from being a pale brownish color to shades of gray and white. The exterior of the shell, except nearest the umbo is covered with a series of growth rings. The interior of the shell is colored a deep purple around the posterior edge and hinge. However, M. campechiensis is slightly larger, and its shell lacks purple coloration on the interior surface. It also lacks any smooth areas near its umbo.
Hard clams are common in sandy bottoms throughout the Indian River Lagoon.
They are also farmed commercially from Indian River County northward. Other important growing areas for clam aquaculture in Florida are Cedar Key in south Florida, and Lee and Charlotte Counties on the west coast of Florida. Owing to their commercial importance, the typical lifespan of Mercenaria is approximately between 4 and 8 years of age, the peak of their commercial marketability. In northern areas of the geographic range, growth in M. mercenaria occurs only during the summer when water temperatures approach 20 C, the optimum growth temperature for this species. In southern areas of the range, growth is more continuous.