Editors

5 Interesting Facts You Might Not Know About Diamonds

EditorsApr 10, 2020

5 Interesting Facts You Might Not Know About Diamonds

Editor-in-Chief Michelle Graff recaps a webinar in which she learned more about the stones’ formation, inclusions and the oldest diamonds on Earth.

20200410_552_carat_diamond_copy.jpg
This 552-carat diamond was recovered from the Diavik Mine in Canada’s Northwest Territories in 2018, and holds the title of largest diamond ever found in North America. Canada is home to the oldest diamonds on Earth.
Last week, I wrote a blog post containing a list of 10 jewelry-related movies to watch while you’re safe at home to give both myself and our readers a break from coronavirus-related news.

I had a great deal of fun doing it, and it served as a much-needed reminder of how much I like to just write, not necessarily about a controversy or a lawsuit, or with clicks in mind, but just for the sheer pleasure of finding an expressive way of sharing something I enjoy.

With that in mind, I’m having fun again this week, this time by sharing five facts about diamonds gleaned from a webinar.

On Thursday, geologist Evan Smith, a research scientist at the Gemological Institute of America, held the first in what is going to be a series of online “Knowledge Sessions” presented by GIA.

The webinars will feature presentations on gemology from scientists, field gemologists and educators, continuing next Thursday with Mike Breeding, GIA senior research scientist, talking about identification methods for lab-grown diamonds.

(GIA is currently building a web page for its Knowledge Sessions; we will share it as soon as it is available.)

Smith’s talk, “The Unique Story of Natural Diamond,” focused on what makes the hardest substance on Earth—and one of the world’s most popular gemstones—so interesting to geologists.

I’ve interviewed and written about Smith’s research here and there over the years; he was the lead author of an article on blue diamonds that landed on the cover of Nature, a scientific journal, in 2018, and his diamond research made the cover of Science in 2016.

He alluded to both these studies in his presentation and taught me a few new things about diamonds as well.

Please feel free to comment below if you’ve learned anything, or if you just feel like saying hello. You also can view the presentation in its entirety on YouTube.

1. Diamonds form deeper in the earth than other minerals.

Most minerals including corundum (ruby and sapphire) and beryl (emerald, aquamarine and morganite) form in the Earth’s crust, which is the layer upon which we all live.

But not diamond, which Smith said is “completely exotic … because it is formed much deeper in the Earth,” beneath the crust at depths of 150-200 kilometers (93-124 miles) in the base of old, thick continents.

Some go even deeper than that, forming at the boundary between the Earth’s mantle and its outer core. These are known as superdeep diamonds.

(For those needing a visual refresher on the layers of the Earth, I found this diagram to be helpful.) 

 
Smith said “very energetic” volcanic eruptions that come from below 200 kilometers bring diamonds to the surface. They are a sort of “accidental passenger” in these explosions.

With them, they carry valuable information in their mineral inclusions, which most commonly include kyanite, garnet and olivine.

Diamond inclusions can help researchers understand the distribution of elements in the Earth’s layers, for example, or when plate tectonics started.

“The diamond is surprisingly good at preserving these materials,” Smith said. “It’s very hard and durable, and good at keeping things from diffusing, or leaking, out of it, and diffusing, or leaking, into it.

 “There’s a tremendous of information trapped in these diamonds.”

2. Superdeep diamonds were completely misunderstood until a few years ago. 

For many years, diamonds that form at depths greater than 200 kilometers were believed to be small and never gem quality. 

But in the past four years, Smith said, researchers have found that many large, high-quality diamonds—Type IIa diamonds (stones with top color and clarity) and Type IIb diamonds, which are gray or blue because of the presence of boron—are actually superdeep stones. 

Evan Smith and a team of researchers studied offcuts from Type IIa diamonds, like this 404-carater, to gain a better understanding of the elements in Earth’s deep mantle. Their research landed them, and this diamond, on the cover of Science magazine in 2016.
Evan Smith and a team of researchers studied offcuts from Type IIa diamonds, like this 404-carater, to gain a better understanding of the elements in Earth’s deep mantle. Their research landed them, and this diamond, on the cover of Science magazine in 2016.

One example of a superdeep diamond is the 404-carat rough diamond recovered from the Lulo Mine in Angola in 2016 (pictured above). Immediately found to be Type IIa and D color, it was the biggest diamond ever known to come from Angola.

The 813-carat Constellation diamond from the Karowe mine in Botswana also is a superdeep diamond, as is the famous Hope diamond and, of course, the largest diamond ever found, the 3,106-carat Cullinan.

Smith said superdeep diamonds are identifiable by the presence of high-pressure mineral inclusions like Ca-pv, calcium perovskite.

3. There are more diamond types than you might think.

Generally, when we talk about diamond types in the trade, we think of Type IIa or Type IIb, terms that speak to a diamond’s physical appearance, its color and clarity and, thereby, its value.

But to geologists like Smith, there are also eclogitic and peridotitic diamonds, two terms I had never heard prior to Thursday’s lecture.

Peridotite and eclogite are two types of rock found in the Earth’s mantle, and diamonds can form in both. These are not superdeep diamonds but the ones found closer, relatively speaking, to the surface of the Earth, also known as lithospheric diamonds.

Peridotite is an igneous rock and is the predominant rock type found in the mantle. If researchers find olivine inclusions in a diamond, then it tells them the host rock was peridotite.

A metamorphic rock, eclogite is much less common. The presence of kyanite inclusions in a diamond indicates it formed in eclogite rock.


In 2018, Smith and a group of researchers completed a two-year study on included blue diamonds, like this 3.81-carat stone, that shed lights on how and where blue diamonds form. It was featured on the cover of Nature. (Photo credit: Robison McMurtry © GIA)
In 2018, Smith and a group of researchers completed a two-year study on included blue diamonds, like this 3.81-carat stone, that shed lights on how and where blue diamonds form. It was featured on the cover of Nature. (Photo credit: Robison McMurtry © GIA)

4. The oldest diamonds in the world are found in Canada.

Smith’s presentation included a timeline (who doesn’t love a timeline?) that illustrated just how old diamonds are relative to the history of, well, everything. 

The Earth dates back 4.5 billion years while the planet’s oldest rocks, found in Northern Quebec, are 4.3 billion years old. 

The oldest diamonds follow at 3.5 billion years old and, like the Earth’s oldest rocks, come from Canada, a fact I already was aware of after hearing Karen Smit, another GIA research scientist, speak about the GIA’s Diamond Origin Program back in the fall. 

Smit said the oldest diamonds studied by geologists so far have come from the Diavik mine, which Rio Tinto owns and operates in partnership with Dominion Diamond Corp. 

 Related stories will be right here … 

Some of Earth’s “younger” diamonds can be found at the Argyle (1.6 billion years old) and Ellendale mines (1.4 billion years old) in Australia, and in Sierra Leone, where the Zimmi diamonds are a spry 650 million years old.

To put this in perspective: All these diamonds are older than the Atlantic Ocean, which opened up when supercontinent Pangaea began to break apart about 200 million years ago, and the dinosaurs, which died off 65 million years old.

5. Pliny the Elder had something to say about diamonds.

Smith opened up his talk with a quote from Pliny the Elder, a Roman philosopher and naturalist who lived about 2,000 years ago: “Diamond is the most valuable, not only of the precious stones, but of all things in this world.” 

And he concluded it with a quote from himself that I liked: “Every diamond tells a story from a place we can’t go and from a time long since passed.”

I’ve now shared a Pliny the Elder quote; my week is complete. 

Have a great weekend everyone, and stay safe. 

Michelle Graffis the editor-in-chief at National Jeweler, directing the publication’s coverage both online and in print.

The Latest

Jemma Wynne Forme Toggle Necklace
CollectionsJul 25, 2025
Piece of the Week: Jemma Wynne’s ‘Forme’ Necklace

Anne Hathaway was seen wearing the toggle necklace three times while filming scenes for “The Devil Wears Prada 2.”

September Hong Kong jewelry show
Events & AwardsJul 25, 2025
Pre-Registration Open for September Hong Kong Show

Jewellery & Gem World Hong Kong is scheduled for Sept. 15 to 21, and buyer pre-registration will be available until Sept. 7.

Bulgari Celestial Mosaic spinel necklace
FinancialsJul 25, 2025
LVMH Sales Slip in H1 Amid ‘Prevailing Uncertainties’

Renovations at Tiffany & Co. stores ate into profits in the company’s watch and jewelry division.

rio-article photo-diamond.jpg
Brought to you by
Taking the Moment Head On: How Rio Grande Champions the Present & Future of Fine Jewelry

As a leading global jewelry supplier, Rio Grande is rapidly expanding and developing new solutions to meet the needs of jewelers worldwide.

Mark and Candy Udell
Events & AwardsJul 24, 2025
2 Retailers to Receive 2026 Gem Award for Lifetime Achievement

Mark and Candy Udell of London Jewelers will receive the honor at the 24th annual Gem Awards next March.

Weekly QuizJul 25, 2025
This Week’s Quiz
Test your jewelry news knowledge by answering these questions.
Take the Quiz
De Beers marine mining vessel the SS Nujoma
SourcingJul 24, 2025
De Beers Sees Diamond Production Sink 36% in Q2

While struggles continue at the mining and trading end of the pipeline, consumer demand for diamond jewelry is holding steady.

Francesca Villa Fantasia Collection The Crab Pendant, The Mermaid Pendant, Keep Dancing Seahorse Pendant, Keep Dancing Ladybug Pendant, Secret Dreams Pendant, The Puffer Fish Takes Flight Pendant
CollectionsJul 24, 2025
Francesca Villa Adds Dimension to Her Intaglio Characters

The “Fantasia” jewelry collection turns the intaglio animals from her “Close Encounters” collection into 3D characters.

an instructor and a student in a bench jewelry classroom
Brought to you by
Investing in the Next Generation of Bench Jewelers

The Seymour & Evelyn Holtzman Bench Scholarship from Jewelers of America returns for a second year.

Breitling’s special Eagles Super Bowl watch on gold bracelet
WatchesJul 24, 2025
Breitling Drops Super Bowl Watch Honoring the Philadelphia Eagles

The special Classic Avi Chronograph 42 with an Eagles-green dial is limited to 59 pieces, a nod to the Super Bowl Philadelphia just won.

Stock image of crime scene tape
CrimeJul 23, 2025
JSA Warns of Violent String of Smash-and-Grabs in California

JSA has received reports of mobs swarming jewelry stores, driving cars into the storefront or smashing through the windows.

Silvia Furmanovich Kasmir Collection Carnelian Bracelet and Sketch
CollectionsJul 23, 2025
Silvia Furmanovich’s ‘Kashmir’ Collection Is a Tribute to Northern India

The “Kashmir” collection features centuries-old craft techniques made in collaboration with the region’s master papier-mâché artisans.

Bench jeweler holding a bracelet and a tool
IndependentsJul 23, 2025
Montreal’s Ecksand Eyes Move to SoHo

Creative Director Erica Bianchini shared why the jeweler is looking to expand into the U.S. and how it’s putting Canadian craftsmanship on the map.

LAFD Fire Station 44 and Fire Station 16
IndependentsJul 23, 2025
IJO Raises Nearly $37K for LA Fire Relief

Two Los Angeles Fire Department stations plan to use the donations to upgrade their equipment and tools.

A Vanitas by Hannah Martin and Guy Berryman Sothebys
CollectionsJul 22, 2025
Jewelry With a Rock ‘n’ Roll Aesthetic Heads to Sotheby’s London

Next week, the auction house will kick off a selling exhibition of jewelry by British artist Hannah Martin and Coldplay’s Guy Berryman.

Cover of the book “Flawless: Inside the Largest Diamond Heist in History”
SourcingJul 22, 2025
Antwerp Diamond Heist Documentary Coming to Netflix

“Stolen: Heist of the Century” is based on “Flawless,” the book about the middle-of-the-night theft, and will debut on Netflix in August.

Emmanuel Raheb
ColumnistsJul 22, 2025
The Gifting Gap: How to Market Jewelry Beyond the Holidays

Emmanuel Raheb shares the top five gifting moments outside of major holidays that jewelers should build marketing campaigns around.

NY Now
Events & AwardsJul 22, 2025
NY Now’s Summer Market Returns in August

The wholesale trade show’s Luxury Lifestyle section will showcase established and emerging jewelry designers.

Jeweler setting a diamond into a ring
MajorsJul 21, 2025
Rio Grande Expands Personalization Offerings

As demand for custom jewelry grows, the company is expanding its services to support retailers.

National Associate of Jewelry Appraisers Logo
Events & AwardsJul 21, 2025
NAJA’s 2025 ‘Ace It’ Conference To Go Virtual

The mid-year conference for jewelry and watch appraisers is slated for Aug. 9 to 10 on Zoom.

Jacquie Aiche graduated turquoise beaded necklace
TrendsJul 21, 2025
Amanda’s Style File: Graduated With Honors

Graduated stones make for elevated tennis-style pieces and dramatic statement necklaces.

24th Gem Awards Show Logo
Events & AwardsJul 21, 2025
Gem Awards Now Accepting Nominations for 2026

Nominations in the categories of Jewelry Design, Media Excellence, and Retail Innovation will be accepted through July 30.

Lewis Heyman
MajorsJul 18, 2025
Lewis Heyman on Sourcing Gemstones, Post-Retirement Plans

He retired last month after 28 years traveling the world to source the very best gemstones for his family’s jewelry business, Oscar Heyman.

CCWW Designs Multiple Shell Charm Necklace
TrendsJul 18, 2025
Piece of the Week: CCWW Designs’ Shell Charm Necklace

The charm necklace features six nautical charms of shells and coral that founder Christina Puchi collected on Florida’s beaches.

The Plumb Club board members
MajorsJul 18, 2025
Plumb Club Elects New Board Members

The organization elected its youngest vice president as it looks to draw in fresh talent.

Jewelry industry veterans Brad Campbell and John Liebler
TechnologyJul 18, 2025
Brad Campbell, John Liebler Join Clientbook’s Executive Team

Campbell joins the company as vice president of business development while Liebler is the new vice president of operations.

Silver, Gold, and Bronze Medals for Italy Olympic Winter Games
CollectionsJul 17, 2025
2026 Winter Olympic Medal Design Symbolizes Unity

The medals feature a split-texture design highlighting the Games’ first time being hosted by two cities and the athletes’ journeys.

vimeo screenshot.png
Supplier BulletinJul 17, 2025
The INSTORE Jewelry Show 2025: Your Holiday Preparations, All Wrapped Up!

Sponsored by The INSTORE Jewelry Show 2025

×

This site uses cookies to give you the best online experience. By continuing to use & browse this site, we assume you agree to our Privacy Policy