Chrysoberyl gems are typically yellowish green stones that take their name from the Greek 'chryso', meaning 'golden', and 'beryl', meaning 'green'. Although chrysoberyl is the group term, popular varieties are Alexandrite and Cat's Eye. Alexandrite is particularly rare and valuable, and desired for the way it's colours appear differently when in artificial or natural lighting conditions. A cat's eye chrysoberyl, or cymophane as it's also known, is a chrysoberyl that has been polished and smoothed into a cabochon form and reflects a long thin strip light across the middle of it's surface - similar to the effect of contracted cat's pupils.