The most classic blue gemstone is sapphire, and the most highly valued blue sapphires are velvety-blue to violetish-blue in medium-to-medium-dark tones. Deeply saturated blue is also found in spinel and kyanite. There are a number of choices in the lighter blues including topaz, zircon and aquamarine. Tanzanite and iolite are more of a violet blue, while Paraiba tourmaline, apatite and fluorite tend to be blue-green.
Some blue gemstones include: Sapphire, Blue Diamond, Zircon, Iolite, Paraiba Tourmaline (pictured below), Tanzanite, Topaz, Spinel, and Aquamarine