Moonstone is a variety of feldspar that exhibits a striking optical phenomenon known as adularescence, which creates a glowing, bluish or white light that appears to float just below the surface of the stone. This effect is caused by the reflection of light from layers of minerals within the stone, giving it the appearance of moonlight. Moonstones can come in a range of colors, including white, gray, peach, and even rainbow hues, but the most prized variety is the blue moonstone, which has a strong, clear blue sheen. Moonstone has a Mohs hardness of 6, making it relatively soft compared to other gemstones, so it is typically used in beads, cabochons, and jewelry. It is primarily found in regions such as Sri Lanka, India, Madagascar, and the United States.