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Rocktober: Minerals Day of Earth Science Week

October 11, 2021

The beauty of minerals….Gemstones from the William Wallace Stephens Collection. An exhibit being prepped in the Collections space under the Museum. Photo credit Sean Moran.

The Mineralogical Society of America has a Minerals Day site here. The three themes for Minerals Day are Science, Value and Beauty. You can download posters and other goodies at the site. Even better, you can advance your knowledge of mineralogy with talks and events found on the Events page here.

I’m here for the Science part. Minerals are information. Hard-rock geologists (igneous and metamorphic) like myself use the chemistry of minerals as the clues to the entire lifespan of a rock. (Soft-rock, that is, sedimentary geologists use chemistry, but also look at grain sizes of sediments.)

The chemical information contained in minerals allows geologists to measure the temperature and pressure of a magma, as well as the gases present – the mineral chemistry is frozen in place after eruption. Metamorphic rocks preserve the time-pressure-temperature path that they followed. The minerals present also show the temperature and pressure of peak metamorphism. Minerals like zircon provide the best absolute dating answers.  

Minerals have value. If you read my earlier blog about my career, you know that the market value of molybdenum determined some of my career choices. A technological society like ours requires a lot of minerals to run. The tired old adage “if it can’t be grown, it has to be mined,” is still true. But even if it is grown, agriculture and forestry still require petroleum and steel for the machines, phosphates for the fertilizer, and all the specialty metals required to make machine parts. These days, they also require high-purity silica for silicon chips, much of it from Spruce Pine, North Carolina. An excellent BBC article is here. The construction industry would crash if crushed stone were not readily available from an aggregate quarry- roads, houses and cement would not be possible. A lowly mineral like pyrite (iron sulfide, FeS2) is routinely set aside during mining. It’s finding new utility as a semiconductor for solar power, which provides a greener source of energy as well as cleaning up mine waste heaps.

Minerals have beauty. Watch our social media accounts for new pictures. I think you’ll agree on this one.

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