The natural gemstone known for its blue color is sapphire. Sapphires belong to the corundum mineral family and are most commonly associated with their striking blue hues, although they can occur in a variety of other colors except red (which is classified as ruby). The blue color is primarily due to the presence of iron and titanium within the crystal structure. Sapphires are prized not only for their beauty but also for their durability, making them suitable for jewelry, including engagement rings. Historically, they have symbolized wisdom, loyalty, and nobility, and remain highly valued in the gemstone market.