Greek: chalkedon, copperlike, as in the green color of malachite and other copper ores. Revelation 21:19.
Probable Identification: chalkedon is probably dioptase, a hydrous copper silicate that was first found as green euhedral, rhombohedral crystals in the copper mines of Chalcedon. It also occurs in the copper deposits of Arizona, Chile, Congo, Namibia, Peru, Russia, and Zaire
Dioptase has a Mohs hardness of 5 and cleaves easily, which limits its durability and value as a gemstone. The rich green color of transparent to translucent specimens, however, makes them attractive for decorative purposes.
Chalcedony in modern usage is the general name for fibrous varieties of cryptocrystalline, milky to translucent quartz. The principal named varieties of chalcedony include carnelian, a translucent red to reddish-brown chalcedony; sardius or sard, a chestnut brown chalcedony which grades into carnelian; chrysoprase, a translucent, pale apple-green chalcedony; prase, or sage-green chrysoprase; agate, or banded chalcedony in alternating, concentric bands of contrasting color; heliotrope or bloodstone, a green chalcedony with spots and streaks of red jasper; and onyx, a banded chalcedony in parallel layers.
A pale blue variety of chalcedony is also known as blue moonstone, although true moonstones are white varieties of orthoclase and albite feldspars with an opalescent play of colors.
Pious legends claim that bloodstone formed during the Crucifixion when drops of blood fell on green jasper at the foot of the cross. However, bloodstone does not occur naturally in the environs of Jerusalem.
Frazier, Si, & Ann Frazier, 1989. Name that jasper. Lapidary Journal; 43-1: 75-89.
Hurlbut, 1952, op. cit.; 322-324.
Lucas & Harris, op. cit.; 392.
Ralph, Jolyon, 1993-2004. http://www.mindat.org/min-960.html
Schumann, op. cit.; 126-127.
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