Most species can produce purple pearls. Some may appear with brown hues. Apart from pearl oysters, there is a high incidence of purple pearls in clams. Given the sheer volume of reports to P-G in the past few years, quahog pearls are likely more common than many of us once thought. Purple pearls from virginia or japanese oysters are rare, but not uncommon.
The purple occurs normally around parts of the shell, usually where the greatest strength is needed in the least amount of space, very often around the edges where the siphons extended from the shell, or near the attachments.
Am I right assuming this was found while still raw?
It has low value as it is, but may make a terrific piece with a little creativity.
Thank you for posting it.