The NATIONAL GEOGRAPHIC Gemstone Advent Calendar 2025 Kids is a 24-day countdown to Christmas filled with colorful gemstones. Each day, kids can open a door to uncover a new gemstone, complete with a rock dig kit for a hands-on learning experience. This multicolored calendar features gemstones as the filling, making it a perfect gift for curious young minds who love rocks and minerals. With a compact size of 0.1 inches and a theme centered around advent calendars, this product from Blue Marble is sure to delight kids throughout the holiday season.