Mika McKinnon Profile picture
Aug 16, 2018 24 tweets 11 min read Read on X
I’m feeling weirdly hurt by the viral tweet mocking geoscientists for licking rocks.

I get that we’re a bit weird even for scientists and get a bit more blunt with our toolset, but licking rocks is a real strategy. Taste & texture are diagnostic.
Evaporites are soft (scratch with your fingernail), but the easiest way to ID between halite vs sylvite is salty vs sour.

IDing sand vs clay is the cutoff between gritty or not.

Fossils stick to your tongue.

You don’t NEED to lick rocks; it’s just faster & easier.
I don’t lick every wild rock I meet, and licking lab samples is just gross.

But if you’re out doing field rock ID, you already know enough to keep your tongue away from arsenopyrite & don’t waste your time nibbling granite.
Not all geoscientists lick rocks. I’m geophysics — 95% of my rock ID is recreational, & it’s been at least a year since I last licked a rock.

But it’s not an inherently ridiculous concept worthy of mockery.
Epilogue:
Q: But what about that salt-licking scene in Last Jedi? Surely that was ridiculous!
A: No. That was plausible bordering on geo fan service.

And it’s tactically important to know what rocks encompass you unless you’re a fan of dumb ways to die.
Q: What about the Doctor?!
A: Excellent tasting technique.

I don’t remember which episode this is for context, but I’d guess dry former water body with sour-bitter-tangy sylvite (or salty halite, but that’s usually less pucker).
Q: Please critique Jack Sparrow's geology taste test technique?
A: Terrible.

First: WAY too much tongue. It's test, not a snack.
Second: Any rock tough enough to weather into that nice smooth shape isn't one where taste is diagnostic. All you'll get is the seawater coating.
Star Wars: "Well, actually..." follow-up:

Doctor Who: Sediments were dead people, so taste test is EXTREMELY diagnostic. Fossils stick to your tongue; desiccating/sticky texture.

Other pop culture geo taste tests? Ping with gif/clip/still for critique.
Q: ...but won't it kill you if you lick the wrong rock?
A: Do not lick anything with mercury, arsenic, or lead. A few others can still kill you (lookin' at you, villiaumite, torbernite, & chalcanthite), but that's a good starting point.
Bad minerals to lick:

Anything that smells like garlic (arsenic). Even handling is sketch thanks to carcinogenic, neurotoxic powder; burning is bonus bad news.
Arsenopyrite: arsenic + sulfur
Orpiment: arsenic + sulfur
Hutchinsonite: sulfosalt of thallium, lead & arsenic OrpimentArsenopyriteHutchinsonite
Anything with mercury is a slow, painful way to die.

Cinnabar: gorgeous mercury sulphide; also the most deadly mineral on Earth. Do not lick. Do not even touch. Considering it oxidizes to methyl mercury & dimethyl mercury, don't go near it, either. Just turn around. Now. Carved cinnabar vasesCinnabar crystals
Coloradoite: mercury telluride, which are both toxic. Heat it up for a deadly vapour!
Mercury: ...it's mercury. Melts in your hand, then infiltrates and poisons you. So fun, DO NOT LICK.

Really, anything with mercury is just a bad move to lick. Full lick-ban on all Hg minerals. ColoradoiteMercuryMercury melting in a hand
Chalcanthite: water-soluble copper sulfate. Taste is diagnostic (sweet metallic) yet it leads to copper poisoning. So, don't lick, but if you're going to, make it a quick tongue-touch-retreat to minimize exposure. Chalcanthite crystalChalcanthite fibres
Anything with lead is a no-go for licking unless you love the long-term violence of lead poisoning.

Galena: lead. Like, all the lead. So much lead. Don't eat it or huff it. Just smash it with a hammer -- if you get a bunch of smaller cubes, yay, it's galena! Done. Galena
Asbestos (serpentine, crocidolite, grunerite, tremolite, anthophyllite & actinolite) is not inherently deadly to lick, except it'll splinter into your tongue like fibreglass & you'll huff shards into your lungs for long-term damage.

Overall, bad candidate to lick (or pet). fuzzy-looking asbestoshand sample of asbestosAsbestos intrusion
Torbernite: uranium. It's radioactive. Licking anything radioactive is a bad idea. It also has copper for a bonus copper poisoning.

Pitchblende (uraninite) & autunite are also bad choices to lick, but great choices for uranium ores if you need to build a bomb from scratch. small crystals of TorberniteLarge crystals of TorbernitePitchblendeautunite
Villiaumite looks seriously tempting, but is a VERY BAD IDEA. It's cherry red, very soft (scratch with your fingernail) & fluoresces under UV light, so licking is unnecessary for ID anyway.

Licking screws up breathing, heartbeat, circulation, nervous system, & skin. Just no. Villiaumite in a rock sampleVilliaumite crystalsVilliaumite close-up
Q: What about Yukon Cornelius?
A: Licking is a terrible way to ID silver or gold, but from the deleted scenes he was actually looking for peppermint (), which while not a mineral, is something where taste is highly diagnostic.
Eep, don’t mind me, just repairing a branching thread midway through Minerals I Won’t Lick:
Q: You do you, but I’d never lick a rock. Ew!
A: Too late, you’ve already licked several minerals today.

Both salt & ice are naturally-occurring crystals with a definite chemical composition. #sorrynotsorry
Q: Is this stalactite appropriate for personal use?
A: Malachite (green) & azurite (blue) are soft copper-rich mineral that are highly sociable in dilute acids.

No. So much no. It’ll break, but before that the copper poisoning will be a nightmare. Phallic malachite formation
ANY stalactite or stalagmite is going to be composed of an acid-sensitive water-solvable mineral that is porous & not particularly strong. It’s inherent in how they form.

Go ahead & lick if you really want (but it’s not diagnostic), but don’t get too up close & personal.
Errata:
Meat cave .gif instead of this one.

*soluble, not sociable, in dilute acid.

That palmful of silver goo on Don’t Lick Mercury Minerals was gallium, which won’t kill you but still doesn’t need licking to ID.
Q: What about Benton Fraser licking sediment from under a suspect’s fingernail clippings?
A: Unhygienic but effective with beautiful tip technique.

Niter (saltpeter) has diagnostic salty baking soda taste. (It’s in gunpowder, but also common in cured meat & sensitive toothpaste)

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More from @mikamckinnon

Dec 26, 2021
The degree of rage I feel when someone flippantly declares getting COVID is inevitable and we should give up is beyond my ability to politely express.

It’s never too late to make things less bad. Like Climate nihilism, it’s self-destructive bullshit & I have no tolerance for it.
Science is an astonishing tool linking cause and effect, enabling us to create a path to any future we want.

It’s not easy! Untangling details can be lifetimes of effort to get right. But the harder part is picking a future, then doing the work.
It’s daunting. We need to do the work individually, but we also need our communities, governments, & everyone everywhere else to do the work.

But if we refuse to surrender to suffering?
If we keep struggling to do better?

We have infinite possible futures that are less bad.
Read 5 tweets
Mar 9, 2021
You know the rules:

Most vibrantly-coloured rocks are on the Do Not Lick list, but ALL rocks that are literally radiating are definitely on the Do Not Lick list.
> Record scratch

> Freeze frame of you, the protagonist, contemplating the pros and cons of licking a plutonium puck.

“You’re probably wondering how I got here. It all started when I was strolling around France...”

#YouFindARock.

📷 Roberto Bosi Densely-packed crystals of a pale translucent tan spackled a
You pick up the hunk of densely-packed quartz crystals, intrigued by the spatters of matte black.

“Did you mould?!” you ask the rock incredulously. “No, no, that’s not quite right... what IS this?”

>
Read 15 tweets
Nov 21, 2020
I’m reading a lot of well-intentioned articles that make it clear how many scicomm peeps have no idea disaster risk reduction is a deep field with a lot of research into effective communication.

ProTip: Using fear & shame as motivation backfires when applied to public health.
I can’t write this article (or even thread!) right now as I’m under medical orders to drop my stress levels (ahahahahasob), but...

If you’re writing well-intentioned pieces trying to influence pandemic behaviour, please take some cues from disaster sociology research. It exists!
Fundamental premise:
Vanishingly few people make active choices they believe will endanger themselves or the people they love.

If they’re making “bad” choices, it’s a fundamentally different risk perception. Until you understand how & why, your argument will miss its audience.
Read 7 tweets
Nov 20, 2020
Gritty has found rocks.

They are all safe but boring to lick. It’s a solid selection of common crystals from a rock shop or museum gift store.

I do have a few questions.
If you go outside and pick up a stray rock, it’s probably quartz.

This looks like quartz. Quartz is an excellent oscillator that is piezoelectric & resonates well.

White sand is also quartz, and is near oceans.

Conclusion: Gritty can use quartz as a distributed spy network.
I have questions on this ID.

If it’s rose quartz, it’s about as fun as licking a window for flavour.

But it could easily be pink halite (like Himalayan rock salt!). If it is...? Lick it! Lick it moar!
Read 7 tweets
Nov 19, 2020
I’m stunned that we’re losing Arecibo.

Even if you don’t pay much attention to ground-based astronomy, you know this telescope from pop culture & movies. It’s somewhere special. nature.com/articles/d4158…
This article from just before the closing announcement is fantastic for the context of why Arecibo is so unique:
space.com/arecibo-observ…
I just...

I know we’ve got a lot going on, especially with the mass casualty event scheduled shortly after US Thanksgiving.

But take some time to read the Arecibo tributes as they come out. They won’t be cheerful. But they’ll be heartfelt.
Read 6 tweets
Nov 14, 2020
Irregular reminder that landslides can behave like fluids.

(Thank you for all the pings!)
Landslides get weird when there really big, and can start behaving more like fluids than solids once they’re over the half million cubic meter mark.

...which was pretty much why I wrote a thesis once upon a time: io9.gizmodo.com/why-are-huge-l…
But technically landslide are fluid-like, not fluids.

Why?

Because they’re a mixed mess of materials that act differently when moving than when still. You can’t just sample a tree trunk, some peat, and water to figure out the rheologic properties (how it flows).
Read 9 tweets

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