Garnet: gemstone, abrasive, rare earth element repository?

Garnet from the Adirondacks, NY

Dr. Zirakparvar has set a high bar for us mentors. He introduced his students to their project with a gift of garnet. I suppose my SRMP students are welcome to take home as much coyote scat as they want if they so wish.

I have always loved garnet for it’s beautiful dark red hue (although I now know that it comes in many colors all dependent on associated impurities) and for the fact that I could actually afford the gemstone on meager high school, college, then graduate student salary. After speaking with Lucie, Isaac, and Patrick, I appreciate it even more.  Garnet is the sand in sand paper. It’s a very hard stone with no cleavage which makes it great for sand blasting or for giving a fine polish. It’s formed in many geologic settings and can be used to understand geological processes since its different varieties reflect the temperature and the pressure under which the surrounding rock was formed. And - more germane to my lab visit - some garnets are enriched in Heavy Rare Earth Elements (HREE).

HREE have  so many uses in our modern life from powering your phones to medical imaging.  Currently, China  is the primary source of most HREEs and the process by which we extract HREEs is nasty. After milling (cracking ore and grinding rock into fine particles), HREEs must be extracted and purified using lots of different chemicals. Many HREE sources are often associated with uranium making for some really toxic, radioactive wastes. Feeling guilty yet as you read this off your cell phone?

Alternative sources are being considered like coal fly ash or some clay deposits, but garnet may have some advantages. Alex and his team are evaluating the possibility that
some garnets may provide a source of HREE that is a bit “cleaner” (e.g. no radioactive wastes). And garnet is EVERYWHERE including upstate NY meaning there may be opportunities for local industry.

Dr. Z and his SRMP team have been in communication with a variety of researches at other institutions interested in defining alternative sources of the HREE and have received a positive response. Now they have embarked on an exhaustive literature search to evaluate the potential of garnet as an industrial source of HREE. What are the HREE concentrations observed in garnets? Where are garnet deposits? What % of rock has garnet? And what % of garnet is associated with HREEs? What type of HREEs? Are there associated radioactive elements? How much does it cost to extract garnet from different mines?

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Depending on the results of their research, I may start investing in garnet mines.

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