 Beryllium is found in over 100 minerals , but most are uncommon to rare . The more common beryllium containing minerals include : <unk> ( <unk> ( OH ) 2 ) , beryl ( <unk> ) , chrysoberyl ( <unk> ) and <unk> ( <unk> ) . Precious forms of beryl are aquamarine , red beryl and emerald . The green color in gem @-@ quality forms of beryl comes from varying amounts of chromium ( about 2 % for emerald ) . 
