The earliest man-made mirror was from a polished stone such as Obsidian (a naturally occurring volcanic glass). Glass mirrors were first produced during the third century A.D., and were quite common in Egypt, Gaul, Germany and Asia. Subsequently, metal-coated glass mirrors were invented in Sidon (modern-day Lebanon) in the first century AD. It was not until 1835 that Justus Von Leibig – a German scientist – invented the first modern silver-glass mirror. Mirrors can be made simply by putting a layer of reflective coating on glass sheets which is a convenient material because of its transparency, rigidity, hardness, smoothness, while durability and reflectivity are the main choices of the coating.