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 societies. Tiffany & Co. published these poems "of unknown author" for the first time in a pamphlet in 1870. In 1912, in an effort to standardize birthstones, the (American) National Association of Jewelers (now called Jewelers of America) met in Kansas and officially adopted a list. The Jewelry Industry Council of America updated the list in 1952 by adding Alexandrite for June, citrine for November and "pink" tourmaline for October. They also replaced December's lapis with zircon and switched the primary/alternative gems for March. The American Gem Trade Association added tanzanite as a December birthstone in 2002. In 2016, the