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Posts by Edward S. Grew

Boron: From Cosmic Scarcity to 300 Minerals

Boron is rare in the cosmos because its nucleus is “fragile.” So, how does one get from the interstellar medium, where boron was first produced, to Earth’s upper continental crust where boron is concentrated in deposits containing remarkably diverse suites of boron minerals? Processes that led to the formation of continental crust also concentrated boron, which is preferentially incorporated into melts and aqueous fluids. Deposits with high boron-mineral diversity include granitic pegmatites, peralkaline intrusions, boron-enriched skarns, and evaporite deposits. Despite the loss of boron minerals from the geologic record due to their ready solubility in water and breakdown at low temperatures, the increase in boron-mineral diversity with time is real, and is accelerated during supercontinent assembly.

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Boron — The Crustal Element

Figure 1. This photograph, which was acquired on October 30, 2013 by an astronaut on the International Space Station, shows one of the largest borate mines in the world (Rio Tinto Borax Mine). The mine is located northwest of Boron, California (USA). The borate minerals in the deposit—largely borax, Na2B4O5(OH)4·8H2O, kernite,  Na2B4O6(OH)2·3H2O, and ulexite,  NaCaB5O6(OH)6·5H2O — formed in…

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