of corundum mineral al2o3 from the mohs scale of mineral hardness on the background from connected molecules

al2o3 aluminium apatite background beautiful beauty color connected corundum crystal crystalline decorative expensive gem gemmology gemology gemstone geological geology hardness icon isolated jewel jewelery jewelry luxury material mineral mohs molecules natural nature object oxide pebble pink precious purple raw red rock rough ruby scale semiprecious shine shiny specimen stone structure surface symbol texture textured treasure uncut vector violet white