The artist is Marcie Poirier, and her company is Wildabout Wampum. The pieces (both pendants and earings) are carved from Quahog and Queen Conch shells.
"Marcia creates her works by meticulously sculpting the rare purple sections of the Quahog shell and the vivid pink hues of the Queen Conch.[taken from her information card]. Contact information available on her website.
Purple Quahog shells occur only in specific areas where they absorb amythest on the ocean floor, making them prized finds for Marcia's jewelry.
Queen Conchs, meanwhile are larger shells found primarily in regions such as Florida, Bahamas, and similar tropical areas.
In Marcia's works, the Quahog and Conch shells are ground, carved and sanded. Many are also then accented with sterling silver highlighting."
The piece I'd gotten her to do was of a nurse's cap. It's just beautiful: