PHOTO: Nokia

Yale University industrial ecologist Thomas E. Graedel likes to point out in his lectures that when you hold a cellphone, you’re holding half the periodic table of elements in your hand. The number of minerals used in electronics has ballooned over the years, and now the industry finds itself highly dependent on some substances whose supply is more precarious than we’d like. Graedel was part of a U.S. government committee that looked at the “criticality”—the combination of importance and supply risk—of a number of key minerals. Some of the most critical are found in cellphones. The ones to worry about, says Graedel, are difficult to find substitutes for and are produced only as by-products of something else, so their own supplies are constrained. Gallium and indium fall into that category. Graedel has also been examining the fact that a more affluent global population may cause even common minerals like copper to become scarce.

COPPER

Use: Wires, cables, and general infrastructure

Top suppliers: Chile, United States, Indonesia, Peru

Projected scarcity: Copper is extensively mined and has a huge reserve base, but recent analysis has found that for the world population to attain North American affluence by 2100, more copper would be required than exists in the Earth’s crust.

GALLIUM

Use: LEDs, lasers, solar cells, and RF circuits

Top suppliers: China, Germany, Kazakhstan, Japan, Russia

Projected scarcity: Gallium is a by-product of the production of other, more important metals, and so its supply is entirely dependent on the demand for those other metals.

HAFNIUM

Use: Insulator in cutting-edge chips

Top suppliers: Australia, South Africa

Projected scarcity: Even though it is found in the abundant mineral zircon, hafnium is rarely refined, and there is little production data available. Because its use is so new, it’s hard to say when it might become scarce.

INDIUM

Use: Transparent electrodes that control the pixels in LCD displays

Top suppliers: China, Canada, Japan

Projected scarcity: The price of indium has shot up recently. Unless new resources are found and recycling improves, indium could be scarce by 2020.

TANTALUM

Use: High-performance capacitors in cellphones and cars

Top suppliers: Australia, Brazil

Projected scarcity: Tantalum will probably not be scarce until after 2030. But a U.S. government report notes that suppliers can easily hold capacitor makers hostage to price increases.

TIN

Use: Main component of lead-free solder

Top suppliers: China, Indonesia, Peru

Projected scarcity: It’s mined extensively and has a huge reserve base, so even if lead solder is eliminated worldwide and the world population’s affluence grows, tin will not become scarce.