The metal oxidizes in bulk (beyond the passivation layer) when heated above 500 ☌ (932 ☏), and burns brilliantly when heated to about 2,500 ☌ (4,530 ☏). In air, the surface of beryllium oxidizes readily at room temperature to form a passivation layer 1–10 nm thick that protects it from further oxidation and corrosion. For example, tools and components made of beryllium copper alloys are strong and hard and do not create sparks when they strike a steel surface. When added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron, or nickel, beryllium improves many physical properties. Because of its low density and atomic mass, beryllium is relatively transparent to X-rays and other forms of ionizing radiation therefore, it is the most common window material for X-ray equipment and components of particle detectors. In structural applications, the combination of high flexural rigidity, thermal stability, thermal conductivity and low density (1.85 times that of water) make beryllium metal a desirable aerospace material for aircraft components, missiles, spacecraft, and satellites. The world's annual beryllium production of 220 tons is usually manufactured by extraction from the mineral beryl, a difficult process because beryllium bonds strongly to oxygen.
Beryllium constitutes about 0.0004 percent by mass of Earth's crust. Within the cores of stars, beryllium is depleted as it is fused into heavier elements. It is a relatively rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Notable gemstones high in beryllium include beryl ( aquamarine, emerald, red beryl) and chrysoberyl. It is a divalent element that occurs naturally only in combination with other elements to form minerals. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. Beryllium is a chemical element with the symbol Be and atomic number 4.
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