Thread by @mikamckinnon

Oh no. It’s the most contentious time of the year for geo-folk. I usually stay out of it, but some of these minerals are going to make me stan hard.

Lineup below. Hashtag to Follow or Mute is #MinCup2018

https://twitter.com/tectonictweets/status/1036542948782026753

Round 1: Olivine vs Diamond:

https://twitter.com/tectonictweets/status/1036542953496477696

Olivine is the defending champion. Here’s why it’s badass from my Ode to Olivibe last #MinCup:

https://twitter.com/mikamckinnon/status/914920082320404480

But diamonds... Diamonds are a more unlikely champion.

Ignore the social/economic burden of diamonds, because it’s not the poor lil minerals’ fault that humans have been terrible over the sparkly.

Instead, let’s talk mineral properties.

Diamonds are dead simple: They’re Carbon.

As a geophysicist forced to memorize chemical composition by sadistic petrologists, I appreciate being able to scrawl “C” for full credit.

Plus, it’ll never be confused with it’s allotrope, graphite. Easy ID is my friend.

Q: How do you ID diamond when it hasn’t been cut & polished into a sparkly wonderland?
A: Rub it against something. Does the mineral scrape your thing? How about that other thing? And that one? If it scrapes EVERYTHING, thar be diamond because it’s literally the hardest material.

Q: But I don’t wanna scrape shit!
A: Fine. Toss it in fire. Or a pool of lava. Liquid lead? Whatev, you ain’t melting it because diamonds are tough fuckers with the highest melting point of any mineral at 4090°C

Q: Diamonds are tough, got it. But why?
A: Diamonds have an EXTREMELY dense crystalline structure (densest atom packing of any mineral). This means toughness, but it also means ridic heat conduction.

Have a diamond nearby? Touch it.

It’s cooler than the surroundings. Science!

Q: Pfft, forget practicality, I’m here for the sparkle-rainbows!
A: Diamonds are transparent over the greatest number of wavelengths (they’re clear), but also have excellent fire, with luster from greasy to adamantine depending on cut.

How?
Total internal reflection

Every diamond is an optics lesson. The cut determines how light bounces around — angle, depth & number of faces influences how much sparkle you’ll get.

You cannot cut a gorgeous diamond without understanding optics. Every diamond ring is #SciArt.

But wait! Just in case you’re STILL not sure you have a diamond, you can flash a UV light at it because diamonds fluoresce!

Diamonds typically fluoresce light blue, but sometimes white, yellow, orange, or red.

How diamonds form can be beyond trippy.

Imagine an asteroid. It has graphite in it. Now slam it into the Earth in a violent cataclysm of doom.

That’s how you get Lonsdaleite, a diamond polymorph with graphite crystal structure (& a rare mineral named for a woman).

But normal diamonds come from kimberlite pipes.

Kimberlite pipes are a volcanic structure we can find now, but they don’t happen anymore. Because...?! Stop asking, just get digging for diamonds!

What we know:
Diamonds form in the mantle.

Kimberlite pipes violently brought diamonds to the surface by covering 100+ miles within hours, or they would’ve degraded into graphite.

How?
Uh... gas, maybe? Except where did the gas come from??

My vote for Round 1 of #MinCup2018:
Fuck Olivine, it won last year.

Diamonds are the hardest, most heat resistant, densest, & clearest mineral, plus they have neat heat conductivity, fluorescence, & luster. The badass origin story is just bonus.

#TeamSparkle

Aside: I wear a ring of reclaimed heritage diamonds with different cuts, thus different sparkles.

A sunbeam hit it on my flight earlier & I was captivated making the light dance.

Diamonds: For when your inner cat takes over. Or when your inner unicorn needs to restock rainbows.

Q: I can only imagine a cut, sparkly diamond. What does a rough diamond look like?

A: Colour depend on trace inclusions or plastic deformation of crystal structure. Usually clear, but can be white, black, brown, grey, yellow, orange, or rarely blue, green, red, pink, or lilac.