Pen pearl is a term used for pearls from the shell species Pinna. This species is found in the waters of the Indian and Pacific Ocean and also in the Mediterranean. These shells produce both nacreous and non-nacreous pearls. The pearls often exhibit a dark grey to black body color with overtones of bright green, blue, purple, silver, and pink. The common name of this species refers to the black coloring along the margins of the interior of the shell. Externally the shell is dark grayish brown or green, though white spots are common across the shell. Adults usually reach between 20 and 25 cm (7.9 and 9.8 inches) in height. Our photographs have been enlarged to show details. Most details shown in the large image are actually not visible to the naked eye. We have made the image as close as po.
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