Geochemistry, Mineralogy, Petrology & Volcanology
Mike Jollands

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.

#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…

Do you have a favourite obscure mineral? Want to write about it? Contact us and give it a go!

#mineralmonday : gadolinite-(Y)

#mineralmonday : gadolinite-(Y)

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

What is it? Gadolinite-(Y),Y2FeBe2Si2O10

Gadolinite: From Rob Lavinsky, – CC-BY-SA-3.0, via

What’s it made of?: It’s a silicate (a mineral containing silicon (Si) and oxygen (O)) also containing yttrium (Y), beryllium (Be) and iron (Fe). Yttrium is a rare earth element – somewhat of a misnomer as in general they aren’t really that rare.

Is it dangerous? It can contain some uranium and thorium, both of which can emit radiation when they decay to other elements. Probably more dangerous if thrown – it’s pretty dense (about 4x heavier than its equivalent volume of water)

Is it pretty? Not really, unless you like greasy looking, opaque, blackish lumps. No judgement.

What’s it named after? Named after a ‘who’ not a ‘what’ – it was named for the Finnish chemist Johan Gadolin, who discovered yttrium. He also had the element gadolinium named after him.

Johan Gadolin, seen here in his natural habitat on a postage stamp. Source:

Wait, so why didn’t they name yttrium after him? Well, ten years earlier a sample of an unknown rock had been found at Ytterby in Sweden, and named for the village, the name more or less stuck when Mr Gadolin identified what it was.

Do any non-Scandinavian countries get to be involved? Not really – much like the Eurovision song contest, the Scandinavians had a near complete monopoly on the early research into the rare-earth elements.

We are getting sidetracked here, why should we care about this mineral? The whole group of rare earth elements are becoming really important these days – we need them for loads of modern technological uses, but some of the most important are rechargeable batteries, really strong magnets, etc. The looming threat of a trade war between the USA and China, who currently hold the vast majority of the world’s supply of these elements, will only make people more interested in minerals that contain them.

Do you have a favourite obscure mineral? Want to write about it? Contact us and give it a go!

How does a crystal become a mineral?

How does a crystal become a mineral?

There are some crystals that we are all familiar with. Look at an analogue clock (you may need a screwdriver and/or a hammer, and the watch owner might not be too happy) and you will probably find quartz – a crystal with silicon and oxygen arranged in a well-ordered three dimensional pattern. We can also describe quartz as silicon dioxide, which describes its chemistry – one silicon for every two oxygen. Another crystal you may not know, but you may well have in your possession, is gallium nitride – made of gallium and nitrogen bonded together into a rigid network. This crystal is the key to blue LEDs, the final piece in the red-green-blue puzzle that is necessary to make white light. This discovery was so important that it led to a Nobel prize.

Gallium nitride. Source:

So silicon dioxide is also known as quartz (or maybe cristobalite, coesite or tridymite depending on its exact structure), but what is gallium nitride also known as? Unfortunately, nothing. This is because it is a crystal, but not a mineral, and only minerals can be named (officially at least – feel free to name any crystal you like and see if it catches on). The difference? Nature. In the laboratory, we can (and do, frequently) mix together different chemicals, maybe heat them up and squeeze them, and form weird and wonderful crystals. Only when this happens naturally do these crystals get elevated to the status of minerals, and as such, get their name. Since silicon dioxide is found in nature, it’s deemed a mineral (of quartz it is!), while gallium nitride is man-made, so is not given this honour.

There are basically two requirements for a crystal to become a mineral – it has to be substantially different from already existing minerals, and it has to exist in nature (which includes other planets, moons, meteorites and so on) and not be man-made. The last point is a tricky one. Imagine, for instance, a crystal that forms during a forest fire that has been ignited by a person. The crystal is more-or-less natural, but the cause of the fire was not. Is this a mineral?

Quartz, or silicon dioxide. CC BY-SA 2.5 license. JJ Harrison ( via

Luckily, there is a panel of forty-something mineralogists who make these complex decisions for us. Based on exactly no evidence, I imagine it looks something like the way in which new popes are chosen, where they all gather in the tallest tower of a natural history museum, and a puff of smoke emerges when the new mineral has its name. Or maybe they use skype.

So let’s say you have your new mineral, it ticks all the boxes. Planning on naming it after yourself? Unfortunately, there is an inbuilt narcissism check- this generally isn’t allowed. Naming it after a company is frowned upon, but still apparently possible, so ample opportunity for sponsorship (maybe there is some money to be made selling the rights to googleite, mcdonaldsite?). If you want to name it after someone famous that’s OK, just take out the spaces between their names. So go ahead with donaldjtrumpite, for his outstanding services to science (hmmm).

Information without wild speculation is available here. Happy new-mineral hunting!