The precious stone traditionally associated with 40th anniversaries is the ruby. Known for its intense red color, the ruby symbolizes love, passion, and commitment, making it an apt choice for a significant milestone like the 40th wedding anniversary. Rubies are a variety of the mineral corundum, and their rich hue comes from the presence of chromium. These gemstones are not only beautiful but also durable, scoring 9 on the Mohs scale of hardness. Due to their rarity and striking appearance, rubies hold great value and are considered a symbol of enduring love.