Usually very light in color-- either white, pink, greyish or blue-chalcedony is a translucent or transparent cryptocrystalline variety of quartz almost always used in cabochon form for gems. It is most commonly found in the deep recesses of volcanic rocks and in Antiquity the most prized variety came from Chalcedon in Bithynia in Asia Minor. The Egyptians, Romans and peoples of the Holy Land frequently carved intaglio gems into it, preferring the milky white variety above all others. Medicinally, Chalcedony is said to have the power to drive away fevers, to cure or prevent diseases of the eye (especially cataracts) and to aid in the relief of gallstones. It was one of the amulet stones used by the ancients to banish bad dreams. Modern science has developed the technique for changing chalcedony's color with a variety of dyes, which makes it a popular stone for jewelry. Its colors are generally of the soothing variety, and those who chose to wear the stone are blessed with a peaceful and equable disposition.