The correct answer is option 2: Emerald. Emerald is a gemstone that contains beryllium metal. Beryllium is a chemical element that is a silvery-white metal and is relatively rare in the Earth`s crust. It is not commonly found in gemstones, but it is present in emeralds.

Emeralds are a variety of the mineral beryl, which is composed of beryllium aluminum cyclosilicate. The vibrant green color of emeralds is a result of traces of chromium and vanadium present in the crystal structure. Beryllium, along with other elements, contributes to the formation and coloration of emerald gemstones.

Topaz (option 1), Ruby (option 3), and Blue Sapphire (option 4) do not contain beryllium metal. Topaz is an aluminum silicate mineral, Ruby is a red variety of the mineral corundum, and Blue Sapphire is a blue variety of corundum. These gemstones do not have beryllium in their chemical composition.

In summary, if you are looking for a gemstone that contains beryllium metal, option 2: Emerald would be the correct choice.