The original Japanese cultured pearls, known as akoya pearls, are produced by a species of small pearl oyster, Pinctada fucata martensii, which is no bigger than 6 to 8 cm in size, hence akoya pearls larger than 10 mm in diameter are extremely rare and highly priced.
Pearl ວັດຖຸບູຮານຂອງຍີ່ປຸ່ນ, ທີ່ເອີ້ນວ່າເພັດ akoya, ແມ່ນຜະລິດໂດຍປະເພດຂອງໄຂ່ມຸກຂະຫນາດນ້ອຍ, Pinctada fucata martensii, ເຊິ່ງບໍ່ມີຂະຫນາດໃຫຍ່ກວ່າ 6 ຫາ 8 ຊມຂະຫນາດ, ດັ່ງນັ້ນ, akoya ມີຂະຫນາດໃຫຍ່ກວ່າເສັ້ນຜ່າກາງ 10 mm ແມ່ນຫາຍາກແລະ ລາຄາສູງ.