Thorium metal 99.9%
Thorium metal 99.9%
Thorium is a common element widely distributed across the earth and typically concentrated in the heavy sands which serve as ores for the rare earth metals. But however common it may be in nature, chemically tied up with other elements such as it is, it might as well all be on the moon. Look high, look low and nowhere can a person buy a gram or two of this “common” metal. Is it because it’s radioactive? Well, yes and no. Thorium is so weakly radioactive that carrying a lump with you poses about as much of a threat to human health as getting an X-ray every other year. You’d have to stand next to a piece of thorium the size of a building before radioactivity levels would become a concern.
But a perfect storm of qualities combines to doom this metal into obscurity. First is the unfortunately fact that thorium has few uses for which other metals aren’t suitable. It is expensive to isolate. It is reactive chemically (it “rusts” easily in air). And, oh yeah, it is radioactive. However weak its energy output may be that certainly doesn’t help it gain acceptance commercially.
A century ago one could buy lanterns which had metallic filaments coated with thorium dioxide, which when heated gives off a light bright enough to rival an incandescent bulb. But then came along widespread adoption of electricity leaving this one singular use orphaned. A specific type of welding uses rods that have a small amount of thorium alloyed in to control electrical arcing; a pretty obscure use that also happens to be in decline as newer formulations replace even this meager demand.
That necessarily leaves the element collector looking to fill his 90th hole a supreme challenge unless he or she is willing to settle for a thoriated rod or a teensy, corroded piece of foil. Beyond those options there really is absolutely no commercial source for this metal.
Understandably, we are very happy to have located a little of this precious resource. Like our protactinium samples, the thorium was laboriously extracted from uraninite and then painstakingly purified over many steps to achieve a small quantity of the pure metal. As it was refined chemically out of the retorts and test tubes came not neat shiny metal bars but metallic powder. This was then pressed at many atmospheres in a confined space to reach its final metallic state as pictured.
The quantity available and the cost make it impractical to sell by the gram. The pieces in the photo weigh approximately 75 milligrams each (give or take 20mg). They measure about 3mm on their longest side and are about 0.5mm in thickness. Thorium slowly tarnishes in open air and will lose its luster. For this reason we recommend long-term storage in mineral oil.