Beryllium
Beryllium is a metal of steel-gray color, very light and hard, but extremely brittle. It can be rolled or drawn only under special conditions.
Pure beryllium is used in the production of windows for X-ray tubes; as components of nuclear reactors; in the aerospace industry; in military manufacturing; as a target for cyclotrons; as electrodes for neon lamps, etc.; as a deoxidizer in metallurgy
Source: "Explanations to the Harmonized System of Foreign Economic Activity of the Russian Federation (HS FEA Russia)" (prepared by the Customs Union of the Russian Federation) (volume 3, sections XII - XVI, groups 64 - 84)