My mother was found dead after she collapsed when getting out of bed. It is unsure how long before she was found, anywhere from 30 minutes to several hours. The funeral home director stated that he could not figure out why her nail beds were black. My mother was a heavy smoker. The black color was under the nails? It was difficult to find a polish to cover this. What was this?

Lentigo maligna melanoma is relatively rare. It arises from a lentigo maligna on an exposed skin surface and usually occurs between ages 60 and 70. This lesion looks like a large (3- to 6-cm) flat freckle of tan, brown, black, whitish, or slate color and has irregularly scattered black nodules on the surface. It develops slowly, usually over many years, and eventually may ulcerate. This melanoma commonly develops under the fingernails, on the face, and on the back of the hands.

This is only one condition associated with discoloration under the finger nails. Possibly her family doctor was treating her for a medical condition and could lend a better insight on this for you.

I doubt that that was the actual situation as expressed above-you would have seen this yourself if you had visited her regularly. If it occurred peri-mortem/post mortem I'd say it was related to death/delay after death (how long did it take to find her?).