I just checked with a pair of calipers. The diameter is 7.3 mm in every direction I spun it give or take a few hundredths of a millimeter. If it helps, I tried candling it.
I just got back from a trip to Hawaii. While I was there I bought some earrings as a souvenir. A free “pick a pearl” was included with the purchase. The jewelry store employee swore it was an Akoya pearl but he would not be a reliable source. I know these tend to be freshwater pearls, but would...