~Four days to fully immerse yourself in gemstones, including the pre-sale of the new "Gemstone Encyclopedia 3D Stickers," special offers for posting on social media, and photo spots~ KARATZ Co., Ltd., which operates " KARATZ Gem Magazine ," Japan's largest specialized gem information media, and " KARATZ STORE ," a specialized online store for gemstones, will be holding a limited-time summer pop-up store at " 2k540 AKI-OKA ARTISAN ," a creative space under the elevated railway tracks between Akihabara and Okachimachi stations on the Yamanote Line, for four days from Thursday, July 30th to Sunday, August 2nd, 2026. At the venue, in addition to displaying and selling a wide variety…