Hi Caitlin,

Actually, the GIA considers 0.25mm a thick nacre. What you find in your average department and jewelry store has less than that. Until recently, 0.35mm was the "Mikimoto standard" under which they would not market a pearl as Mikimoto brand (those were sold as Blue Lagoon brands). However, the GIA standard lowering coincided with the Mikimoto Endowment of the GIA pearl scholarship and Mikimoto's own lowering of its minimum to the same limit. Also please note that 0.25mm is only equivalent to one layer of fingernail polish not two. And 9 months have somewhat more than 90 days (around 275, as if that made much of a difference).

Zeide