 Beryllium is a chemical element with symbol Be and atomic number 4 . It is created through stellar nucleosynthesis and is a relatively rare element in the universe . It is a divalent element which occurs naturally only in combination with other elements in minerals . Notable gemstones which contain beryllium include beryl ( aquamarine , emerald ) and chrysoberyl . As a free element it is a steel @-@ gray , strong , lightweight and brittle alkaline earth metal . 
