The shade of pink in some of these crystals is so delicate it's only just pink. In others it's as rich as candy floss (cotton candy). Some feature black, white, yellow and grey mineral inclusions.
Pink opal and precious opal have an almost identical chemical composition. Common opal as the pink variety is correctly known lacks 'play of colour'. Both stones are made up of hardened silica gel (water and quartz) and contain five to ten percent water in tiny pores. The pores are so minute they cannot even be seen under a regular microscope.