Cell phones, electric cars and lasers require a few essential, but rare, elements that have been produced and marketed mostly by China. Now, new USGS research on timeworn samples from the U.S. western mining era show potential new sources of the fundamental ingredients used in 21stcentury technologies.
USGS scientists are reanalyzing rocks, minerals and associated mine tailing samples – some collected 120 years ago – to assess their rare and critical elements, which could become potential for economic development.
Rare earth elements (or metals) are a set of 17 chemically-related elements, and are specifically made up of the fifteen lanthanides plus scandium and yttrium. Scandium and yttrium are considered rare earth elements since they tend to occur with the lanthanides in nature and exhibit similar chemical properties.
Despite their name, rare earth elements (with the exception of the radioactive promethium) are relatively plentiful in the Earth’s crust, with cerium being the 25th most abundant element at 68 parts per million (similar to copper). However, because of their geochemical properties, rare earth elements are typically dispersed and not often found concentrated in economically exploitable ore deposits.
In addition to studying the nature and occurrence of rare earth elements, the USGS is conducting research on the distribution, occurrence and understanding of a range of new technology critical (strategic) minerals such as indium, tellurium, gallium and all others. These rare metals are of increasing interest due to their usage in many new materials such as LCD screen, solar cells and medical imaging devices.
“Without rare earths we’d be back to having black-and-white cellphones again,” said Ian Ridley, director of the USGS Central Mineral and Environmental Resources Science Center in Denver, Colo.
Laser Ablation Technology Helps Tap into Old Samples
Laser ablation is one method USGS scientists are using to discover pockets of unearthed and untapped critical mineral and rare earth resources.
“I get to shoot rocks with lasers to discover new (or old) information about rare metals contained within the rock,” said Alan Koenig, the USGS scientist in charge of the tailings project. “We can tease out from the rock not only what it’s made of, but we can discover a story about how it formed.”
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is the technique that is allowing USGS scientists to quickly analyze old (and new) rocks for the wide range of chemistry of interest to many aspects of USGS projects and society. The technique utilizes a high energy laser to “zap” a small hole in the sample and introduce it into the mass spectrometer (the ICP-MS part of the system). In doing so, the sample in virtually any form (mineral, powder, or even frozen liquids) is directly analyzed without the need for complicated, time-consuming or dangerous acid dissolving of the material. While the systems are still expensive to acquire, and commonly require highly-trained staff to develop and operate, LA-ICP-MS is becoming a common tool in geology, forensic and materials facilities.
Laser Ablation Lab
The USGS has been a world leader in the development of methods related to the analyses of geologic and earth related materials. Laser ablation ICP-MS is no exception. The USGS LA-ICP-MS Facility located in Denver, Colo., is one of the premier facilities for a wide range of applications and methods development. The USGS LA-ICP-MS facility is one lab where scientists are working on discovering and comprehending untapped resources, and new contributions to natural resources in the United States.
Links to USGS programs/publications that feature Rare Earths