Chrysoprase is a green translucent variety of the mineral chalcedony. Of all the varieties of chalcedony, this gemstone is most prized. The name comes from Greek (chrysos = golden). The typical apple green color (which varies from yellow-green to grass green) is caused by aqueous silicates (or oxides) of nickel (eg kerolite, pimelite). The color may fade in sunlight. The green stones were among the most valuable and popular in ancient times. Chrysopras was already used by the Greeks and Romans. It gained significant popularity especially in the 14th century, when it was left by Charles IV. to decorate the St. Wenceslas Chapel in Hradčany and also the chapel in Karlštejn. Newer is the decoration of Sanssouci Castle in Potsdam. It is used in jewelry for rings, earrings and brooches, for the production of smaller decorative items.