Smithsonite is a mineral form of zinc.
Credit: farbled | Shutterstock
Bluish-silver zinc is a workhorse element, crucial to life and important in many industrial processes that often go unseen.
This metal is positioned on the Periodic Table of the Elements with the atomic number of 30, and was used by Greeks and Romans in ancient times, according to the Royal Society of Chemistry. But zinc was not as popular as copper or iron, according to a 2006 paper in the open-access journal Ancient Asia; it boils away at a lower temperature than is required to extract it from its ore, so ancient smelting techniques were not up to the task of isolating zinc.
Nevertheless, archaeologists have found a handful of zinc artifacts, including a sheet of zinc from Athens that dates back to 300 B.C. Today, the metal is used mostly as coating for steel and iron to prevent rusting, a process called galvanization. Incredibly, galvanization dates back centuries — The Royal Armouries of Great Britain include a collection of armor from India made in the 1680s which was galvanized by dipping in molten zinc.
Just the facts
According to the Jefferson National Linear Accelerator Laboratory, the properties of zinc are:
- Atomic number (number of protons in the nucleus): 30
- Atomic symbol (on the Periodic Table of Elements): Zn
- Atomic weight (average mass of the atom): 65.38
- Density: 7.134 grams per cubic centimeter
- Phase at room temperature: Solid
- Melting point: 787.15 degrees Fahrenheit (419.53 degrees Celsius)
- Boiling point: 1,665 F (907 C)
- Number of isotopes (atoms of the same element with a different number of neutrons): 25; 5 stable
- Most common isotopes: Zn-64 (48.6 percent naturally occurring), Zn-66 (27.9 percent naturally occurring), Zn-67 (4.1 percent naturally occurring), Zn-68 (18.8 percent naturally occurring) and Zn-70 (0.6 percent naturally occurring)
Zinc was discovered before it was officially discovered. In 1746, German chemist Andreas Marggraf (also the inventor of a process to extract sugar from beets) figured out how to isolate zinc by heating carbon and calamine (the stuff in calamine lotion). Marggraf reported the finding in great detail, which earned him credit for the discovery, even though several European researchers had already completed the same feat. An English metallurgist, William Champion, had even patented the process years earlier.
Even Champion was drawing on techniques dating back to the Middle Ages, however. Zinc was first used in China by at least A.D. 1637, and was mined and smelted in India even earlier — by the ninth century B.C., at least, according to the 2006 research published in the journal Ancient Asia. At first, ancient people used zinc ores mostly to make brass (an alloy of copper with zinc). However, zinc was recognized as a metal in its own right by 1374 in India, according to the International Zinc Association (IZA).
So what is zinc good for? About half of the 12 million tons produced a year go to galvanization, according to the IZA. Seventeen percent of zinc's annual production goes into brass and bronze, and yet another 17 percent is used in die-casting, the production of metal parts with the use of molds. The rest goes to other manufacturing uses, such as creating roofing materials, or into chemical compounds such as zinc oxide. This white powder shows up in everything from sunscreens to solar cells to nuclear reactors, where it helps prevent corrosion.
Zinc also has a role in health. It's an essential mineral that keeps the body's enzymes humming. Zinc deficiency can slow growth and hamper the immune system, according to the National Institutes of Health. Some of the weirdest side effects of zinc deficiency involve abnormalities of smell and taste, because the metal is crucial to these processes.
- Zinc may be the only known cure for the common cold — sort of. According to the NIH, medical studies have found that if zinc lozenges or spray are used within 24 hours of the onset of symptoms, the length of a cold is reduced. However, these over-the-counter treatments should be used with caution, because no optimal dosing has been established, and too much zinc from nasal gels or sprays has been linked to permanent loss of the sense of smell. Might be worth keeping the cold for another day or two.
- Zinc makes up 70 milligrams of every kilogram of the Earth's crust, on average, according to the IZA.
- A zinc compound, zinc gluconate, can take the sting out of deadly box jellyfish venom by stopping the leakage of potassium from blood cells, according to 2012 research.
- There's zinc in your pocket: Pennies are 97.5 percent zinc and only 2.5 percent copper.
- Most people get plenty of zinc through their food. But zinc supplements may be useful for women who struggle with depression and irritability before their periods. A 2013 study found that supplementing at least 15 milligrams a day of zinc was associated with a lower risk of premenstrual syndrome, or PMS.
Zinc's role in life can't be understated. In fact, the element appears to be a crucial component of the meeting between sperm and egg.
A December 2014 video, published alongside a study in the journal Nature Chemistry, shows the fireworks of fertilization as an egg releases "sparks" of zinc after enveloping a sperm. Researchers are still exploring this phenomenon, but they have discovered that without the zinc eruptions, the egg cannot develop.
Zinc "might even be working as a master switch to tell the cell when to divide," study co-author Thomas O'Halloran, a chemist at Northwestern University in Chicago, told Live Science.
Cells typically concentrate zinc until there are about as many zinc atoms in the cell as there are base pairs in the organisms' genome, O'Halloran said. But some cells concentrate more than that.
In its last hours before full maturation, the egg cell starts taking in zinc, O'Halloran and his colleagues have found, going from about 40 billion zinc atoms to about 60 billion. About 15 percent of the total zinc ends up in vesicles, little packets squirreled away right under the cell's surface.
When the sperm and egg meet, these packets get ejected. It's possible that the zinc release creates a barrier against the entry of more than one sperm, which would be fatal to the developing embryo. But that's yet to be proven, said study co-author Teresa Woodruff, a professor of obstetrics and gynecology and fertility preservation at Northwestern University.
The zinc fireworks could have real-world applications for women dealing with infertility, Woodruff told Live Science.
"In IVF [in vitro fertilization], you need to be able to select which egg has the highest likelihood of giving rise to a healthy offspring," she said. The zinc "sparks" could potentially hint at the egg's vitality, allowing doctors to choose the best fertilized eggs for implantation in the uterus.
Cells in the brain, particularly the memory region known as the hippocampus, also hoard zinc, as do insulin-releasing cells in the pancreas, O'Halloran added.
"We think we've actually discovered something that will be broadly useful in understanding how cells work," he said. What's more, the research highlights how life uses the raw materials of the Periodic Table in order to thrive.
"We tend to think of inorganic things as not being alive," O'Halloran said. "But when they're found to play a central role in the way life works, it's really intriguing and kind of counterintuitive. Life, from its very earliest point has been adapting and using the minerals and inorganic components of nature, and has carried that on even at the highest stages of evolution."
- Jefferson Lab: The Element Zinc
- Los Alamos National Laboratory: Zinc
- Royal Society of Chemistry: Zinc