Chrysoprase is best known for its distinctive green colour.
It's a type of chalcedony which is a cryptocrystalline variety quartz. This means its crystals can only be seen with the aid of magnification.
The finest grade chrysoprase gemstones can be mistaken for emerald. The mineral's colour comes from impurities of nickel.
Chrysoprase was mentioned by the ancient Roman author and naturalist Pliny the Elder in his encyclopedia "Naturalis Historia".
The Chapel of Saint Wenceslas in Prague is decorated with chrysoprase.