Critical raw materials: Toxic, rare and irreplaceable

Antimony is a gray metalloid, which is often used to harden other metals. The origin of its name is disputed. One speculation claims it derives from "anti" and "monos," which collectively mean "a metal not found alone". Antimony often occurs as a compound. In ancient Egypt and ancient India, it was powdered and used as medicine or compressed into sticks for use as cosmetics — especially eyeliner.

Baryte, which means "heavy" in Greek, is a barium sulfate, commonly found in lead-zinc veins in limestone. Its crystals, which often grow in sand and contain grains of sand within their structure, form into clusters known as baryte roses. Baryte can be clear, or can shimmer in hues of yellow, red, green or pale blue.

The incredible staircase-like shapes that characterize bismuth are the result of the outside growing faster than the inside. Another unusual feature of this brittle crystalline metal is that it is denser in liquid form than in a solid state. When it freezes, bismuth — just like water — expands. It is used in fire detectors and extinguishers, as well as in cosmetics and paints.

Cobalt takes its name from subterranean German goblins known as "Kobolde." Centuries ago, German miners inhaled toxic fumes released from rocks while extracting ores during the melting process. When they fell sick, they blamed it on goblins. In 1960 cobalt caused a series of deaths when breweries in Quebec added it to their beer to help ensure a good foam. Nearly 50 people died from heart failure.

Fluorspar is a colorless, transparent mineral that often contains impurities and hydrocarbons, and which can change color and glow when exposed to ultraviolet light. It is frequently used to lower the melting point of metals during processing. Fluorspar occurs as a compound with lead and silver ores, as well as alone in limestone.

Gallium melts at just 29 degrees Celsius (84 degrees Fahrenheit), making it the only metal to melt when held in a human hand. By contrast, it doesn't start to boil until it reaches the unusually high temperature of 2,204 degrees Celsius. Gallium is generally produced as a byproduct of bauxite and is used for semiconductors. When added to other metals, gallium causes them to become brittle.

Lithium is the lightest metal of all and the least dense solid element. If it weren't reacting with water, it would float on its surface. Lithium is one of the three elements — besides hydrogen and helium — to form during the Big Bang. Current theories suggest there should be three times more lithium in the universe today than is actually the case. It is not known where the rest of it went.

When added to steel, niobium creates an outstanding structural strength, even though it only represents 0.1% of the alloy. It is used in jet engines, superconducting magnets and MRI machines. Niobium is named after the Greek goddess of tears, Niobe, daughter of mythological King Tantalus, whose name was later given to the metal tantalum. Niobium and tantalum are always found together in nature.

In 1546, scientist Georgius Agricola wrote about German Ore Mountain miners who, during the melting process, reported a black and "hairy" metal that reduced their tin yield like a "wolf devours a sheep." Foam appeared on the surface, binding to their tin inseparably. The miners named the metal wolffram, meaning wolf's foam. The name was later dropped for the Swedish alternative: tungsten.