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Well, actually... No.

All table salt is rock salt, or in geology-talk, halite. All halite is formed as an evaporite, precipitated out of evaporating saline solution such as an ocean or a lake.

Y'know, like Utah's Great Salt Lake.
Q: But aren't all the salty lakes just old oceans?

A: Not necessarily. The Great Salt Lake is a remnant of Lake Bonneville, which was a lake off & on (but never a sea) for the last 80,000 years, concentrating minerals from glacial-melt runoff.
To be fair, some of the largest brine lakes are isolated fragments of ancient oceans.

The Dead Sea was a bay of the Mediterranean Sea when it formed 3 million years ago until it was uplifted 2 million years ago, then has been a lake ever since.
Bonus weirdness:
It's possible to have a brine pond INSIDE an ocean. They're nicknamed “hot tubs of despair” as they kill pretty much everything that swims in. Fun!

Learn more: latimes.com/science/scienc…
📷Jack Cook / @WHOI Diagram of a pit in the sea floor filled with high saline water
@WHOI Even weirder:
Death by "brinicles", ridiculously fast-freezing icicles formed when super-chilled high-salinity brine spills into the ocean. (They'll really only kill wee fishies caught in them, not humans, but still, ICY FINGERS OF DEATH!)

Learn more:
@WHOI Q: Hey, why do some edible salts look & taste different if they're all halite?

A: Halite is cubic crystal of of sodium chloride (NaCl), but it can have traces of other elements (calcium, magnesium, potassium, copper, iron...) or even clay or ash.
@WHOI Bonus DIY science trick:

The perfect cubical structure of halite is why you can sprinkle salt on the table then use it to balance the shaker at a wonky angle.

📷Theodore Clutter (crystals), Steven Earle (diagram), David Smart (shaker) Salt shaker leaning at a strange angle
@WHOI Q: What's the difference between a sea & a huge brine lake?

A: Common names are inconsistent.
In technical jargon:

Seas attach to oceans in periods of high sea level. If they're uplifted above sea level, they become lakes

Lakes are inherently transient: they form, mature & die
@WHOI Q: But where did the first salt come from?

A: Saline solution of dissolved Na+ & Cl- ions from other rocks. You can't get evaporite minerals without liquid to evaporate!

But after it forms, you can cycle crystallizing salt & dissolving into saline over & over.
Bonus evaporate fun time:
Minerals precipitate out of solutions in very specific orders. With saline solutions, it’s first calcite, then gypsum, halite, & finally sylvite. It creates distinct bullseye deposits.

We don’t eat it, but sylvite tastes neat: tangy-bitter Top view of a bullseye with calcite on the outside and sylvite in the inside, then the same deposit in cross-section with calcite outside-deep and sylvite center-shallow
My fav salts are the Badwater Basin salt flats in the Mohave Desert.

For thousands of years, desert rain washes down the mountains to create temporary lakes that evaporate and leave behind one of the largest (& most photogenic) salt flats in the world.

📷 Don Smith/Getty Beautiful flat white valley floor completely covered in white crystals with a overlying hexagonal pattern. Mountains are visible in the far distance.
Q: What's the deal with those gorgeous hexagonal ridges in salt flats?!

A: Salt crystallizing from saline oozing out of mudcracks, which are hexagonal from thermal contraction & crack propagation (same as Giant's Causeway or cheesecake cracks)

📷Salar de Uyuni, Boliva by Getty Endless white crystalline salt flats with hexagonal cracking under a pink sunset glow
Q: What about non-edible halite, salt but not "table salt"?

A: Anywhere you get NaCl precipitation but lots o' contaminates. Deep sea brines (hot tubs of despair! hydrothermal vents!), altered through metamorphism, even the mantle!
My desire to taste-test space rocks is going to get me killed one day.

More salt that’s still halite but you’d never find on a table (due to scarcity & maybe danger):
Salty bedtime story by @MaryRobinette, including tasting notes on sylvite’s distinctive bitter tang (KCl, the secret to low-sodium salt blends) and the earthiness of trace magnesium (like Himalayan pink salt).

Delete/repost: CW child death
@MaryRobinette What about colour?

Himalayan: pink from iron oxide, & more
Alaea: red-pink from volcanic clay
Murray River: pink-orange from algae carotene
Maras: pink from potassium, manganese, & more
Kala Namak: (baked) pink from iron oxide
Prague Powders: (salt blend) dyed pink
@MaryRobinette Smoked: (baked) brown from wood smoke
Celtic: grey from tidal clay
Kala namak: (baked) red-black from charcoal, bark, herbs
Lava, Cyprus: jet black from added activated charcoal
Jugyeom: (baked) blue/purple from bamboo & clay
Persian: blue optical illusion from compression
@MaryRobinette Q: Let's get weirder with salt environments!

A: If you have a it's a big ol' evaporite deposit (of halite & more minerals), you can get salt tectonics (halotectonics) that uplift salt domes (diapers).

Very trippy geophysics.
@MaryRobinette Mud volcanoes often have disproportionately high amounts of evaporites (including halite) & clays as light (low-density) minerals "float" compared to rock.

Learn more: agupubs.onlinelibrary.wiley.com/doi/pdf/10.102…
@MaryRobinette *diapir grumbleGrowlGrouch

Where you are influences your source of common table salt (vs fancy foodie salt).

Syracuse, NY supplied most of American in 1800s.
Solnitsata, Bulgaria supplied salt for 4700‑4200 BCE Balkans.
Middlewich's vacuum brines produces most modern UK salt.
Q: More exotic salts, pls?

Kostroma: (baked), black from rye residue, cabbage, herbs
Kala manak: purple-black from greigite (iron sulfide)
Kona deep water sea salt: white from halite, but with a LOT of other minerals
Sal de Gusano: (smoked), brown from worm larvae & chilis
Q: Have you licked halite you found outdoors?

A: Yes, many times, from tiny crystal rims of tide pools to the vast salt flats in Utah.

Given industrial contamination, I probably shouldn’t lick as many wild rocks as I do, but eh. 🎶Still alive!🎶
Q: Well actually, wasn't the entire planet ocean if we go back far enough?

A: That's complicated as we have very few rocks to whisper stories of that first billion years.

We have 4 billion year old continental rock.
We have hints of a first ocean 3.8-4.4ish billion years ago.
Q: Hey, I need a new salt-related nightmare to roll in to the weekend.

A: Gather 'round for the story of Lake Peigneur. Everyone lives, yet "mine flooded by punctured submarine salt dome" is on my list of Worst Ways To Die.

More: damninteresting.com/lake-peigneur-…
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