Some Beryls display chatoyancy and are cut en-cabochon to Cats-eyes, and are a collectors gem. Beryls are beryllium-aluminium-silicates. As pure beryl, they are colourless, but coloration is derived from impurities - into green, yellow, pink or blue. Iron colours beryl into Blue- the most beautiful sea-blue Aquamarine.
Traces of iron, and minerals containing uranium, give a colourless beryl an intense yellow tone - the Golden beryl.
Beryl is the mineral and family name for the well known gemstones, emerald and aquamarine. Lesser known varieties include goshenite (colorless), morganite (pink), Heliodor (yellow) and bixbite (red)