Galena — Lead Ore
Lead (Pb) is one of the first metals to have been used by humans, dating back to about 6500 BC. Lead pipes have been discovered dating to the time of the Pharaohs in Egypt. The ancient Egyptians also used lead in the glazes on their pottery.
Lead is a naturally occurring metallic element usually associated with other ore minerals (primarily those of zinc, silver and copper) such as pyrite, sphalerite, quartz and barite. Trace amounts of other elements including gold are sometimes found with lead ore. The most common ore mineral of lead mined in the United States is galena with the chemical symbol PbS. Galena is lead sulfide with a hardness of 2.5 on the Moh's scale – actually quite soft – but it is VERY heavy with a specific gravity of 7.4 to 7.6. To put that in perspective, it weighs about 700 pounds per cubic foot!
Although lead is by far the most reclaimed industrial metal in the world, demand for it continues to outstrip the supply. Each American uses 11 pounds of lead each year – some of which is provided from recycling. Lead can not be manufactured. Like all other natural minerals it must be mined.
NOTE: In its sulphide mineral form – galena – lead IS NOT harmful to touch or handle.
The primary use of lead is in the construction of lead-acid batteries. If you drive a car, you own a battery. To produce NEW lead used for batteries and other products we use every day, galena must be refined to remove and recover other metals. To accomplish that, the ore is smelted in a blast furnace with limestone and coke (a "cooked" coal) to remove impurities. Many of the other metals recovered as byproducts in the refining process also have value and are used in making other common consumer products ranging from copper wiring to film to jewelry.
Recycled lead, because it is easily re-melted and refined, is a significant part of our lead supply. In the US, about 80% of all lead is used in automotive-type, lead-acid batteries. In automobile applications, batteries provide electrical power for starting your engine and continuing electrical power for accessories such as lights,radios and CD & DVD players. Lead storage batteries are still the most dependable way to store energy for future use and play an important role in the operation of electric cars. More than 95% of all lead-acid batteries in the US are recycled.
Lead is also an outstanding material for radiation shielding. Major progress in dental and medical applications of radiation use for x-rays and for imaging diagnostics such as CAT scans is the direct result of the use of sophisticated lead shielding to protect both patients and healthcare professionals. Special lead-lined rooms in hospitals make life-saving radiation treatments safe and possible.
Why is lead important to you? Where would you be without your computer? Lead used in your computer and TV screen protects you from radiation and enhances the image. And how about cellular phones and microwave ovens? Lead solder used in electronic circuitry helps make those and many other products possible that make your life a bit easier and more comfortable.
Some of the world's finest china is glazed with lead, including the official White House dinnerware in many administrations. Throughout the ages, stained glass pieces such as cathedral windows have been held together by malleable lead cames, which can be relied on to endure for centuries. In fact, many of the colors themselves were created with lead and the finest stemware is still made from lead crystal.
To learn more about how we produce and use lead today, visit the website of The Doe Run Company. Doe Run is located in Missouri and is the leading producer and recycler of lead in the US. Another site for additional information about lead is the International Lead Association.
PROPERTIES OF LEAD
|Atomic Weight||207.2 amu|
|Weight||0.4092 lb/cubic inch|
2.44 cu. in. of cast lead weighs1 lb.
707 lb. per cu. ft.
1 sq ft of lead sheet 1 in. thick weighs 59.2 lb.
1 square meter lead sheet 1 mm thick weighs 11.36 kg
|Volume||1 lb. = 2.44 cubic inches|
1 kg = 88.28 cubic centimeters
|Melting Point||621.5 °F|
(Check out our Periodic Chart of the Elements for additional information.)