Pure germanium is a lustrous, gray-white, brittle metalloid with a diamondlike crystalline structure. It is similar in chemical and physical properties to silicon, below which it appears in group IVa of the periodic table . Germanium is very important as a semiconductor. Numerous alloys containing germanium have been prepared.
Germanium forms many compounds.
Since the oxide is transparent to infrared radiation, it has found use in optical instruments. Other halides are known. A sulfide and numerous organo-germanium compounds are known. The element was called ekasilicon by D. I. Mendeleev , who predicted its properties with striking accuracy from its position in his periodic table. It was first isolated from argyrodite in 1886 by Clemens Winkler, a German chemist, who gave it the name germanium.