There are many blue stones that are used in jewellery, but some of the most common and popular ones are: Sapphire: This is a precious gemstone that has a deep blue hue and a high hardness. It is often associated with royalty, wisdom, and loyalty. Sapphires can also come in other colours, such as pink, yellow, or white. Aquamarine: This is a semi-precious gemstone that has a light blue to greenish-blue colour and a good clarity. It is named after the Latin word for seawater and is believed to have a calming and soothing effect. Aquamarines are the birthstones for March. Blue Topaz: This is a semi-precious gemstone that has a bright blue to sky blue colour and a good brilliance. It is often treated with heat or irradiation to enhance its colour. Blue topaz is the birthstone for December and is thought to bring joy, love, and peace. Tanzanite: This is a rare and valuable gemstone that has a violet-blue to indigo colour and a high refractive index. It is only found in one place in the world, Tanzania, and was discovered in 1967. Tanzanite is a pleochroic gemstone, which means it can show different colours depending on the angle of light. These are just some examples of blue gemstones that are used in jewellery. There are many more, such as azurite, turquoise, lapis lazuli, blue lace agate, kyanite, blue apatite, larimar, blue chalcedony, blue zircon, and blue tourmaline. Each one has its own unique characteristics, meanings, and uses.