Germanium: The Rare Element in Fiber Optics, Night Vision and Solar Cells

What germanium is

Germanium is a rare element present in trace amounts in most rocks, because it bonds readily with iron and organic materials.

• Earth as a whole averages about 14 parts per million, but most of it is in the core (37 ppm); the crust holds only about 1.5 ppm.
• It never occurs as a native metal, but about 30 germanium minerals are known. Refined, it is grayish-white and metallic.
• It is a semiconducting metalloid, with electrical properties between a metal and an insulator.
• Discovered in the late 1800s in silver ore near Freiberg, Germany, and named by chemist Clemens Winkler after his country. Its first commercial use came after World War II, when Karl Lark-Horovitz of Purdue University found its semiconductor properties.
• It is essentially nontoxic, except for a few compounds — though one or more parts per million dissolved in drinking water may cause chronic disease.

What it's used for

• Fiber optics (the largest use worldwide): added to the silica glass core of fiber-optic cable to raise its refractive index and cut signal loss over long distances.
• Infrared optics (the leading U.S. use): lenses and windows for night vision and thermal imaging used by the military, law enforcement, border patrol and search-and-rescue teams, including on unmanned aircraft.
• Solar cells and electronics: single-crystal wafers form the base of multijunction solar cells, the most efficient available as of 2014 and preferred for space; also in high-brightness LEDs for LCD TV backlights and vehicle lights.
• Plastics: germanium compounds catalyze PET resin for polyester fabric and clear plastic bottles.
• Other: gamma- and X-ray detectors, some chemotherapy, metallurgy.

The Denver Federal Center's 8-megawatt solar installation, part of its goal of becoming the most sustainable government campus in the United States by 2020. U.S. General Services Administration.

Where it comes from

• Germanium occurs in many ore deposits — seafloor volcanogenic massive sulfide, porphyry copper, epithermal, sedimentary exhalative, Mississippi Valley-type and Kipushi-type zinc-lead-copper deposits.
• It is recovered as a by-product of zinc, silver, lead and copper ores, mostly from the zinc mineral sphalerite. Less than 5 percent of the germanium in zinc concentrates is recovered, and because smelters blend ores, production is hard to trace to deposits.
• Coal: germanium-rich coal ash (up to 1.1 percent) was found in 1933 in Britain's Durham Coalfield; recovery from power-station flue dust began in the 1950s, then faded. Today 30 to 50 percent of primary production comes from lignite in China, Russia and Uzbekistan. The largest known germanium-rich coal deposit, in the Yimin coal field of Inner Mongolia, holds an estimated 4,000 tonnes.

Supply and demand

Reserves are hard to estimate for a by-product, but in 2013:

Exploration suggests another 5,600 tonnes in Inner Mongolian coals and 6,000–7,000 in the Russian Far East.

• Production has grown dramatically but swings widely in an opaque market. In 2012 the world produced about 128 tonnes — 70 percent in China, 4 percent in Russia, 2 percent in the United States, plus Canada, Spain, India, Finland and Australia.
• Outside China, the main producer is Teck Metals of Canada (40 tonnes in 2007), partly from ore from Alaska's Red Dog mine, a germanium-rich zinc mine.
• Several U.S. companies make germanium-based semiconductor equipment, lighting and communications materials, and recycling services.

Securing future supply

Germanium's military and commercial importance makes it a critical material. Silicon can substitute in some electronics, LEDs and infrared uses, usually with poorer performance — and there are few substitutes in defense and law enforcement.

• Zinc residues: exploration and mine expansion are active, and some zinc deposits may hold enough germanium to extract during smelting. Kipushi-type deposits in Africa could be rich sources but are remote and little explored.
• Coal: germanium-bearing coal and flue dust are the largest resource by volume, but tapping them depends on better technology and higher prices.
• Recycling: little germanium is recovered from consumer products, but manufacturing scrap from fiber optics, infrared optics and substrates is reclaimed at high rates — 70 to 80 percent for U.S. fiber-optic production in 2006.
• Demand, driven by fiber-optic cable, was projected to grow eight-fold from 2006 to 2030.

More: USGS statistics on germanium production and consumption, recycling and history.

Sources

Based on C.N. Mercer, "Germanium—Giving Microelectronics an Efficiency Boost," U.S. Geological Survey Mineral Resources Program fact sheet; a work of the United States government in the public domain. The photograph from the General Services Administration is taken from the fact sheet's PDF; three others, credited to a company, a regional corporation and a Wikimedia Commons user, are left out.