dioptase
/ˌdaɪɑpˈteɪs/
noun
- A bright green, transparent mineral made of copper silicate, often used as a gemstone or collector's specimen.
- The jeweler showed us a small dioptase crystal with a vivid emerald color.
- Collectors prize dioptase for its intense green hue and glassy luster.
- She added a rare dioptase specimen from Namibia to her mineral collection.