Subtitles (120)
0:00Rocks and minerals are known for being tough.
0:02They’re the hard stuff that makes up
the planet, and without them…well,
0:05we wouldn’t have much of a planet at all.
0:07Lots of the minerals on Earth
started out life as liquids,
0:10either dissolved in water or
heated above their melting point.
0:14But occasionally, the minerals can form in
0:15such a way that preserves a few
drops of fluid inside of them.
0:20This primeval liquid isn’t likely to
replace your water bottle any time soon,
0:24but it is more than just a curiosity.
0:27It’s a window into the
workings of the ancient Earth.
0:30So let’s talk about the forbidden mineral water in
these crystals, and why you should not drink it.
0:39The majority of minerals on our planet crystallize
from fluids beneath the Earth’s surface,
0:44and this crystallisation happens
when the pressure, temperature,
0:48or saturation of the liquid reaches the
Goldilocks point for mineral formation.
0:52And that perfect combo of temperature and
pressure is different for each mineral.
0:57For instance, igneous minerals
freeze out of molten lava when
1:00the temperature dips below their melting point.
1:03Meanwhile, sedimentary minerals
crystallize when the concentrations
1:06of their component molecules gets high enough.
1:09Crystals can begin to grow in
a lattice within that fluid,
1:13building up a scaffold of atoms and bonds.
1:15But if there’s anything else
floating around inside that fluid,
1:18it can interfere with the growing crystal,
and cause imperfections in the 3D lattice.
1:24That can make some parts of the
crystal grow faster than others,
1:27which can sometimes result in a bubble of
liquid missing the mineralization party.
1:32And as the mineral continues to
grow, it seals the bubble inside.
1:35Most of this mineral growth happens deep beneath
the Earth’s surface where temperatures are
1:40typically warmer, so when those minerals are
brought to the surface, the rock cools down.
1:45And when the warm liquid inside cools down, it
contracts more than the surrounding crystal,
1:51creating a gas bubble that the
liquid can slosh around in.
1:55Together, these liquid and gas bubbles
trapped inside crystals are called fluid
1:59inclusions, and they can be found in
a surprisingly wide range of minerals.
2:04You can find fluid inclusions in
metamorphic rocks, in the form of
2:07carbon dioxide squeezed into a liquid by the
high pressures at the bottom of the crust.
2:13Lots of sedimentary minerals also
preserve bubbles of groundwater
2:16and hydrothermal fluids inside them, too.
2:19Those bubbles can even contain crude oil.
2:21And it doesn’t stop at sedimentary rocks.
2:24Water can get stuck inside igneous rocks as well.
2:26Gas bubbles are sometimes frozen inside amber.
2:29You can even find water and
gas trapped inside glacier ice.
2:33And yes, glacier ice is a rock, because
it forms basically the exact same way as
2:38limestone does, by compressing lighter
material down into one solid thing.
2:43In this case, snow becomes ice.
2:45In most cases, fluid inclusions
inside crystals are very small,
2:50rarely measuring more than a
tenth of a millimeter across.
2:53But that doesn’t mean they
can’t be useful to geologists.
2:56The presence of fluid inclusions in gemstones
helps gemologists tell the difference between
3:01natural and synthetic stones, and can even
help them determine where those stones formed.
3:06Mapping fluid inclusions in the field can
also help in the search for mineral resources,
3:11since they can be a telltale sign of
the hydrothermal systems that formed
3:15valuable ore deposits that we really want to find.
3:18Plus, heating and cooling the inclusions can
help to reveal their internal composition,
3:23without ever having to break the crystal.
3:25So these fluid inclusions can reveal all
kinds of secrets about the ancient Earth.
3:29Because these bubbles trap air, researchers
have been able to use them to sample the
3:33atmospheric gases during the Cretaceous,
thanks to air bubbles stuck in amber.
3:38They found that the concentration of
oxygen was much higher during that period,
3:43and helped geologists chart its sudden drop from
35% to roughly 20%, around 65 million years ago.
3:50And hydrocarbon inclusions in old sedimentary
rocks can give clues to the migration of
3:55petroleum through those reservoirs, which
could help people find sources of crude oil.
3:59Despite their value to the world of science,
4:01the tiny size of these fluid inclusions
means they rarely get the love they deserve.
4:05But there is one kind of water-trapping mineral
that has become fairly iconic: the enhydro agates.
4:11Agates are essentially colorful
forms of the mineral chalcedony,
4:14which is a kind of fibrous microcrystalline
quartz that forms from silica-saturated fluids.
4:20Agates can be many colors depending
on the mineral impurities inside them,
4:24but the enhydro versions also contain
water and gas on an impressive scale.
4:30These mineral specimens are like fluid inclusions
on steroids: they’re entire geodes that can
4:35contain enough ancient fluid that you can see
it sloshing around, no magnification needed.
4:41Of course, you could break open the geode
to let the liquid come flooding out,
4:46but then your water’s all gone and your
enhydro agate becomes an ‘ex-hydro’ agate.
4:51Instead, if you polish your agate pebble juuuust
right, to get close to the water pocket but
4:56not actually breach it, you can see the fluid
moving around while keeping the pocket intact.
5:01Now, the big bubbles in enhydro agates form
in a very similar way to the microscopic kind.
5:06Agates typically form in spaces that
were once bubbles in igneous rocks,
5:10crystallizing from fluids that
percolate through those rocks.
5:13As the agate geodes grow from
the walls of the rock bubble,
5:17some of those fluids get trapped inside.
5:19Just like with normal fluid inclusions,
geologists have tried to figure out the
5:22composition of enhydro agate liquid, in the
hopes of learning more about their formation.
5:27For instance, in the state of Rio
Grande do Sol in southern Brazil,
5:31enhydro agates are often found
in Cretaceous age volcanic rocks.
5:35Since they had to have formed
after the rock itself solidified,
5:38the agates are thought to be
between 60 and 40 million years old.
5:42Incredibly, when researchers drilled
into some of these enhydro agates,
5:46they extracted what appeared
to be bacterial cells.
5:50Not only that, but the cells seemed
to be moving around erratically,
5:53suggesting that they were still alive!
5:55So had these agates preserved life,
intact, from tens of millions of years ago?
6:02Unlike the single crystals that trap fluid
inclusions in an impenetrable mineral lattice,
6:08agate’s microcrystalline structure
means its slightly porous.
6:12That means that over time,
fluids can move in and out of it.
6:16So the liquid that’s inside
these enhydro agates may not
6:20be the same liquid that helped
to form them in the first place.
6:24And when the researchers looked at the genes
of the bacteria they got from their Brazilian
6:28enhydros, they found them to be closely related to
the kinds of bacteria you get in tropical soils.
6:34You know, the kind that you
get on the surface… in Brazil.
6:39While the enhydro agates are porous to water,
we’re still not totally sure if the gaps are
6:44big enough for bacteria to get in or out,
so it’s hard to say whether the microbes
6:49inside are really really ancient, moderately
ancient, or really not very ancient at all.
6:55Either way, the bacteria still offer a
fascinating window into the agate’s long history.
7:00And regardless of how old they are,
7:02they’re also why you should definitely not
drink this particular type of mineral water.
7:08This month’s Rocks Box subscribers will
receive their own enhydro agate from Indonesia,
7:13each of which is at least 5 million years old.
7:16And if you’ve been hoping to subscribe to our
7:17monthly Rocks Box deliveries but
weren’t able to, you’re in luck!
7:21We were able to open up some more subscriptions.
7:23How many are left when you’re seeing this?
7:25I genuinely don’t know, because
we filmed this in December.
7:28Head over to Complexly.store/rocks
to see if there’s any left!
7:31You can also find lots of minerals a la mine cart,
7:35including our premium samples of
some gorgeous fossil ammolite.
7:38Check all that out and more
at Complexly.store/rocks.
