Metalloid suggested that compounds of silicon, germanium, arsenic, and antimony with B metals, "are probably best classed as alloys". Among the lighter metalloids, alloys with transition metals are well-represented. Boron can form intermetallic compounds and alloys with such metals of the composition MB, if "n" > 2. Ferroboron (15% boron) is used to introduce boron into steel; nickel-boron alloys are ingredients in welding alloys and case hardening compositions for the engineering industry. Alloys of silicon with iron and with aluminium are widely used by the steel and automotive industries, respectively. Germanium forms many alloys, most importantly with the coinage metals. The
Germanium defense stockpile in 1987. Germanium differs from silicon in that the supply is limited by the availability of exploitable sources, while the supply of silicon is limited only by production capacity since silicon comes from ordinary sand and quartz. While silicon could be bought in 1998 for less than $10 per kg, the price of germanium was almost $800 per kg. Under standard conditions, germanium is a brittle, silvery-white, semi-metallic element. This form constitutes an allotrope known as "α-germanium", which has a metallic luster and a diamond cubic crystal structure, the same as diamond. At pressures above 120 kbar, it