Lapis Lazuli is a dark blue stone made up of the mineral lazurite, and flecked with threads of golden pyrite. Throughout history, it has played a major role in trade, medicine and art. Painters were using ground up lapis to make the blue pigment (ultramarinum) for their art as late as the 19th century. During the middle ages, this stone was ground into a powder and given as medicine for ailments of the eyes, depression, general health and to aid pregnancy and childbirth. The Romans believed it to be an aphrodisiac, and the stone was mined and traded heavily during the height of the Persian and Egyptian civilizations for aesthetic and religious purposes.

As far as further mystical properties of the stone go, it is said to be useful for mental clarity and improving your emotional, spiritual, physical and psychic health. It strengthens eyesight if habitually worn, and can help alleviate fevers. Ruled by Venus, it is also a stone of spiritual love.

If a vampire wished to walk around during the day time, they needed to wear a simple amulet set with a lapis lazuli to protect them from the sun's harsh rays. This vampiric characteristic, to the best of my knowledge, came completely from the imagination of LJ Smith. In vampire tales before her time, such a talisman was either unnecessary and ineffective. This element of the story was surely created to allow her vampires to interact with the mortals around them under in the light of day, while keeping the sun as mortal threat at the same time.

But why a lapis lazuli? In all of my research, I couldn't find any mention of a mystical property to make this stone a logical choice. My only guess is that the Lapis Lazuli was chosen for its deep blue color that is reminiscent of the color of the sky right at twilight. Another possible connection to mention, is that lapis lazuli was held sacred to Nuit, an Egyptian star/night deity. This would link the stone with nighttime, which may be the reason for the stone's power. Wearing a lapis on the body could be like carrying the night with the vampire, allowing them to pass through the daylight harmlessly.

If you've found any better connections or information on the Lapis Lazuli that would be useful to this site, feel free to share it and contact me!