What Do Diamonds Tell Us About the Deep Earth? With Mineralogist Kate Kiseeva

[MUSIC] 

[Hikers walk up a huge mountain at sunrise.]

KATE KISEEVA (Assistant Curator, Division of Physical Sciences): It’s very interesting to realize that, despite the fact that below our feet there more than 6,000 kilometers to the center of the Earth,

[Video of the Earth from space.]

KISEEVA: –humans have only managed to drill up to 12.3 kilometers.

[KISEEVA appears on screen, speaking to the camera.]

KISEEVA: We're thinking about these movies where we see drilling up to the earth core.

[Workers move drilling pipes on a drill rig.]

KISEEVA: But in fact, we couldn’t drill even past the continental crust. And therefore,

[Two scientists look at a box of scientific drill cores. Closeups of the rocky drill cores follow.]

KISEEVA: –all the information we can get directly from drilling is very limited.

[KISEEVA sits at a microscope, adjusting it.] 

KISEEVA: Some of the few natural samples that can give us a window into the deep Earth–

[Closeup of a small diamond in a microscope viewing dish.] 

KISEEVA: –are minerals captured inside diamonds. 

[American Museum of Natural History logo appears, over footage of diamonds sparkling. KISEEVA reappears on screen, speaking to the camera. Text appears: “Kate Kiseeva, Assistant Curator, Division of Physical Sciences”] 

KISEEVA: My name is Kate Kiseeva, and I'm an assistant curator of mineralogy at the American Museum of Natural History. I'm curating these halls which you see behind me,

[The camera flies through the Mignone Halls of Gems and Minerals, with a giant amethyst geode sparkling in the center.] 

KISEEVA: and I'm also curating about 100,000 of minerals–

[KISEEVA walks through a hallway of open shelving with large mineral specimens sitting on the shelves. Closeup of drawers of minerals opening.]

KISEEVA: –which are in the archive of the Museum. 

[KISEEVA reappears on screen, speaking to the camera.] 

KISEEVA: Diamond is a very special mineral.

[Diamond rings sparkle with a rainbow of colors.] 

KISEEVA: Probably everybody knows diamonds. They sparkle, they have very high refractive index,

[A pair of tweezers hold up a diamond and rotate it so that the facets sparkle.]

KISEEVA: –and that allows this amazing kind of variation of colors to see–

[A large diamond sparkles with a rainbow of colors from its facets as it rotates on screen.] 

KISEEVA: –when you shine light over them. 

[A diamond saw cuts another diamond on a lathe-like machine, followed by a closeup of some industrial diamond wire cutting through stone in a mine.] 

KISEEVA: Diamonds are the hardest minerals on Earth, and that makes them incredibly important industrially.  

[KISEEVA reappears on screen, speaking to the camera.] 

KISEEVA: There is another angle on diamonds, and this is geological angle. We can study them because they’re some of the deepest minerals on Earth that we have on the surface. 

[An animation of the Earth rotating in space. Orange, yellow, and brown circular layers appear superimposed on top of the Earth.]

KISEEVA: The earth is layered. The top layer is the crust,

[The diagram of Earth’s layers zooms in to just one quarter of the Earth. The outermost layer is blue in some places and brown in other places. Two labels point to the blue and brown parts of this outermost layer, respectively: “Oceanic crust, surface – 10 km,” and “continental crust, surface – 40 km.”] 

KISEEVA: –and there are two types of the crust, the oceanic crust, which is much thinner, and the continental crust, which is significantly thicker and a few tens of kilometers. 

[Those labels disappear, and a new label appears, pointing to the orange-red layer below the crust. Text reads: “Upper mantle, 10-40 km – 410 km.”]

KISEEVA: The next layer is the upper mantle. And the upper mantle goes roughly up to 410 kilometers depth, where there is this very enigmatic and very unusual layer– 

[The previous label disappears, and a new label appears, pointing to the orange layer below the upper mantle. Text reads: “Transition zone, 410 km – 660 km.”] 

KISEEVA: –called transition zone that separates the upper mantle from the lower mantle. 

[The previous label disappears, and a new label appears, pointing to the yellow-orange layer below the transition zone. Text reads: “Lower mantle, 660 km – 2,900 km.” Shortly afterwards, another label points to the yellow center of the Earth. Text reads: “Core, 2,900 km – 6,370 km.”] 

KISEEVA: And then the lower mantle goes all the way into the Earth core. 

[The Earth’s layers diagram rotates to be in the center of the screen. Layers for the crust, upper mantle, transition zone and the lower mantle are visible.] 

KISEEVA: Natural diamonds are really deep. 

[Circles with images of natural diamonds appear between the upper mantle and the very top of the lower mantle. A bracket surrounds them and a label to the left of it reads “Natural diamonds, greater than 120 km.”] 

KISEEVA: They form at depths well beyond 100 kilometers–

[An icon of a drill platform appears on top of the crust layer, drilling only a tiny bit into the crust. Text next to it reads: “deepest drill core, 12 km.” 

KISEEVA: –far deeper than humans have ever drilled. Diamonds are brought to the surface– 

[A drawing of a plume of lava starting in the transition zone appears, and brings the natural diamonds up to the surface on top of the crust.] 

KISEEVA: –by some of the deepest terrestrial volcanoes, and we can study these diamonds– 

[Images of rough, uncut diamonds appear on screen.] 

KISEEVA: –to learn more about the Earth at those depths. 

[A diamond with a geometric bubble-like feature inside of it appears on screen.] 

KISEEVA: When diamonds crystallize in the mantle, they sometimes capture these small minerals– 

[KISEEVA looks at a computer screen where there is a 3D rendering showing what looks like a diamond with small minerals inside of it, highlighted in blue.] 

KISEEVA: –which are located in the same media from which diamond crystallized. 

[Very close up image of the interior of a diamond, with another mineral embedded inside of it, almost like a bubble.] 

KISEEVA: And these little minerals which they are capturing are called inclusions. 

[A hand with a large diamond ring on it.] 

KISEEVA: When you go jewelry shopping and you hear the word inclusion,

[Two people in a jewelry store look at jewelry together.]

KISEEVA: –the jewelers are not particularly happy about those. 

[A jeweler inspects a diamond through a loupe.] 

KISEEVA: And it's usually some impurity, some inconsistency, 

[A jeweler places a diamond into a band of diamonds on a ring.] 

KISEEVA: –something that you want to get rid of.

[KISEEVA reappears on screen, speaking to the camera.] 

KISEEVA: But it's exactly opposite for the geologist, because by looking at this inclusion, especially diamond inclusion, it tells us a story. 

[An illustrated diagram of the Earth’s surface appears. On the left, a wavy frequency line goes from top to bottom. At the top, a label reads “lower pressure, lower temperature” and at the bottom, a label reads “higher pressure, higher temperature.” The layers start descending below the surface, using the same color scheme as the Earth’s layers diagram before. First, in the crust layer, two circles appear, one with an image of a quartz crystal, and one with an image of a feldspar crystal, and they are labelled in text below.]

KISEEVA: With the increase of pressure and temperature as we travel– 

[As the diagram passes below the crust into the upper mantle, two new mineral circles appear. One contains an image of an actinolite crystal and the other contains an image of a spinel crystal, both labelled in text below.] 

KISEEVA: –into the deep Earth, the structure of minerals changes. 

[At the edge of the transition zone, one last mineral circle appears, with a garnet crystal inside and labelled below. All the mineral circles fade away and the screen is split between the upper mantle above in orange-red and the transition zone below in orange. A circle appears in the transition zone with a ringwoodite crystal.] 

KISEEVA: For instance, a mineral called ringwoodite is a very high-pressure form– 

[Another mineral circle appears above ringwoodite in the upper mantle. It contains an olivine crystal.] 

KISEEVA: –of olivine. So if we take ringwoodite– 

[The ringwoodite circle rises from the transition zone upwards into the upper mantle, next to the olivine. As it does, it morphs into an olivine crystal.] 

KISEEVA: –and try to put it at lower temperatures and pressures, it will revert back to the olivine.

[The newly-created olivine circle sinks back down into the transition zone and morphs back into a ringwoodite crystal.] 

KISEEVA: And diamonds allow these inclusions of– 

[The ringwoodite crystal appears embedded inside a rough diamond inside the transition zone. A lava plume starts to bring the diamond to the surface, and inside it, the ringwoodite crystal remains unchanged.]

KISEEVA: –unusual and very deep minerals to be preserved the way they are in the mantle all the way to the surface. 

[A red garnet crystal appears on screen.]

KISEEVA: There are some garnets, beautiful red minerals. 

[A photo of a pale green crystal, a diopside, appears on screen.] 

KISEEVA: There are clinopyroxenes, green minerals. 

[A hand holds up a sparkling green olivine crystal and rotates it.] 

KISEEVA: Olivine, the most common mineral in the Earth upper mantle.

[KISEEVA reappears on screen, speaking to the camera.]

KISEEVA: There are also very rare minerals, minerals that we wouldn't expect to be as an inclusion. 

[KISEEVA looks at a computer screen which shows an x-ray of a diamond which appears white or clear, with small specks of black included minerals inside it, contrasting from the diamond.] 

KISEEVA: We have the structure that is present at depth, 

[KISEEVA reappears on screen, speaking to the camera.] 

KISEEVA: –and we can compare that with the rocks or the minerals that we synthesize in the lab. 

[The camera pans around a laboratory with brightly colored machines with many knobs and readings. Text appears: “Bayreuth Geoinstitute, University of Bayreuth, Germany”]

KISEEVA: And this is an entire new branch of geology which is called experimental petrology. 

[Camera focuses on someone doing something with a welder, and then two people working with a large machine wearing ear and eye protection, and lab coats. Text appears: “Experimental Petrology Lab, American Museum of Natural History, New York.”] 

KISEEVA: Petrology is the study of rocks, and experimental means that we produce this rock in the lab.  

[Gloved hands measure a small amount of a powder into a gold metal tube.] 

KISEEVA: In order to run an experiment, we usually take inorganic components, mix them together, 

[Closeup of a gold tube-like capsule that has been welded shut.]

KISEEVA: and put them in small capsules. Then we apply– 

[Camera zooms in on a machine with a large metal press in the center of it.] 

KISEEVA: –high-temperature and high-pressure to recreate those conditions–

[Closeup of a machine readout ticking up, with a sign that reads “Caution Keep Away.”] 

KISEEVA: –which we expect–

[Pressure gauges increase on dials.]

KISEEVA: –are present in the mantle. And then we can compare it with– 

[Closeup macro image of a tiny black inclusion inside a diamond. A scale bar reads 200 mm.] 

KISEEVA: –the inclusions in diamonds. 

[KISEEVA reappears on screen, speaking to the camera.]

KISEEVA: And in that case, we have a really good, I would say, experimental proof that confirms our natural observations. 

[Close up images of natural diamonds, and inclusions embedded within them. KISEEVA looks at some of these images on a computer screen.] 

KISEEVA: Diamonds and their inclusions give us a really large window into the deep Earth. It's amazing how,

[A hand holds up a small plastic vial with a tiny diamond inside.]

KISEEVA: –by studying them we can actually address– 

[A microscope plate sits with a diamond on top of it, and some other diamonds in the background next to it.]

KISEEVA: –such big questions as the– 

[Drone footage above the separation of tectonic plates in Iceland.] 

KISEEVA: –onset of plate tectonics on Earth,

[A physical model of the convection, or the motion of heat throughout the inner Earth, on display at the Museum.]

KISEEVA: –as mantle convection,

[Drone footage of glowing lava moving slowly over a volcanic landscape.]

KISEEVA: –as the formation of very deep volcanoes, 

[KISEEVA reappears on screen, speaking to the camera.]

KISEEVA: –as the conditions in terms of pressure, temperature as well as oxidation state in the deep Earth.

[Drone footage above steaming geysers.] 

KISEEVA: We know that the concentration of oxygen– 

[Seedlings emerge from soil and sprout leaves.] 

KISEEVA: –in the Earth atmosphere has varied– 

[The Sun shines over the horizon of the Earth as seen from space.] 

KISEEVA: –over the course of our planet’s history.

[KISEEVA adjusts a machine in a laboratory, then moves over to a computer screen to look at the changing graphs.] 

KISEEVA: Looking at the mantle, through diamond inclusions, can help us better understand those changes over time. 

[Credits roll.

Producer

Lee Stevens

Additional Camera

Erin Chapman / AMNH

Lisa Rifkind / AMNH

Rehanna Chandon, Kobie Fowler, and Matt Kohler / AMNH

Denis Finnin / AMNH

Keiji Hammond / AMNH

Shuai Ma, University College Cork

Adobe Stock / Anton, ufuk, Zhanna

iStock / BlackBoxGuild, Byjeng, DuxX, gorodenkoff, Hoptocopter, Kybele, muraviov, Nejc Gostincar, poco_bw, Simon Skafar, spawns, Travel Wild, TUNTI

Images / Archive

Kate Kiseeva

Nestor Korolev

iStock / A_Pobedimskiy, Bjoern Wylezich, Chun Hin LAI, daboost, KrimKate, rep0rter, rgbdigital, stuartpitkin, TommyIX

Wikimedia Commons / Giuliofranzinetti, Jasperox

Music

“Simple Theory” by Alex Deeping (PRS) / Warner/Chappell Production Music

“Mad Scientist” by Peter Christiansen (PRS) / Warner/Chappell Production Music

“Light Momentum” by Alex Depping (PRS) / Warner/Chappell Production Music]

[MUSIC ENDS.]