Chalcedony to as prase. However, the term prase is also used to describe green quartz, and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.) Blue-colored chalcedony is sometimes referred to as "blue chrysoprase" if the color is sufficiently rich, though it derives its color from the presence of copper and is largely unrelated to nickel-bearing chrysoprase. Heliotrope is a green variety of chalcedony, containing red inclusions of iron oxide that resemble drops of blood, giving heliotrope its alternative name of bloodstone. In a similar variety, the spots are yellow instead, known as plasma. Moss agate
Birthstone as "Navaratna" (nine gems). At birth, an astrological chart is calculated, and certain stones are recommended to be worn on the body to ward off potential problems based on the place of these forces in the sky at the exact place and time of birth. While the term "birthday stone" is sometimes used as a synonym for birthstone, each day of the week is also assigned a unique gemstone and these assignments are distinct from the monthly assignments. Birthstone A birthstone is a gemstone that represents a person's month of birth. Birthstones are often worn as jewelry or as a