Geochemistry, Mineralogy, Petrology & Volcanology

#mineralmonday : emmonsite

#mineralmonday : emmonsite

#mineralmonday: your weekly* dose of obscure mineralogy, every Monday** [*not guaranteed; **or possibly Tuesday-Sunday]

What is it? emmonsite, Fe2Te3O9.2H2O

Emmonsite from Moctezuma Mine. Photo by Leon Hupperichs, via

What’s it made of? Iron (Fe), tellurium (Te), oxygen (O) and water (H2O)

I think I remember tellurium from chemistry class – remind me what it is? We can more or less divide the elements into the metals and the non-metals – tellurium is one that sits in between the two groups – it’s a ‘metalloid’. It’s recently become really important for making solar panels.

So can we mine the emmonsite? Actually, the main source of tellurium for solar panels is a by-product of copper refining – this provides about as much as we need at the moment. And also, emmonsite is really rare.

That’s annoying. Is it pretty at least? Yeah, it’s a beautiful apple green mineral that can take different forms – small crystals covering the surface of rocks, little prisms or even some plant-like shapes (see photos).

Emmonsite from Moctezuma Mine, photo by Christian Rewitzer, via

And I guess it’s named after an emmons, what’s that? Samual Emmons – he was an American geologist in the late 1800s. Like Matt Damon, he was from Boston, but quite unlike Matt Damon, the largest glacier in the contiguous USA is named after him (Emmons glacier). Also two mountains (both called Mount Emmons, confusingly).

Seems unfair to have so much named after one person? Yeah. Maybe it’s something to aspire to, but I had a look at google maps and it looks like all the good mountains are already taken…

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Mike Jollands
Mike Jollands is an experimental petrologist at the University of Lausanne in Switzerland. He studies the diffusion and substitution mechanisms of trace elements, making use of high temperature and pressure equipment to simulate volcanic and mantle conditions.

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