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

GIA iD100® Technology
Supplier BulletinJul 03, 2025
Protect Your Customers and Your Business

Sponsored by the Gemological Institute of America

Madison Keys in Brilliant Earth campaign
MajorsJul 03, 2025
Brilliant Earth Names Tennis Star Madison Keys as Its New Ambassador

The 2025 Australian Open champion is the jewelry brand’s first athlete ambassador.

Muse Nordstrom shop-in-shop
MajorsJul 03, 2025
Muse Sets Up Shop in Nordstrom’s New Jewelry Hall

The West Village jewelry boutique’s new shop-in-shop is the cornerstone of Nordstrom’s revamped jewelry hall.

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.

Shree Ramkrishna Exports
SourcingJul 03, 2025
SRK Announces Its Natural Diamonds Are Now Carbon-Negative

This past year, the manufacturer said it recorded below-zero emissions per carat of natural diamond.

Weekly QuizJul 02, 2025
This Week’s Quiz
Test your jewelry news knowledge by answering these questions.
Take the Quiz
Yeprem Golden Strada Statement Necklace
CollectionsJul 03, 2025
Piece of the Week: A Firework of Diamonds From Yeprem

The brand’s “Golden Strada” statement necklace features round, marquise, and pear diamonds that sparkle like Fourth of July fireworks.

Stock image of police cars with their lights on
CrimeJul 03, 2025
JSA Shares Holiday Weekend Security Tips Amid Spike in Burglaries

JSA’s Scott Guginsky provided a list of nine security measures jewelers should observe while locking up for the long weekend.

Jewelers of America logo with meetup, State of the Majors, giveaway and massages
Brought to you by
Jewelers of America is Headed to Las Vegas for JCK 2025

The countdown is on for the JCK Las Vegas Show and JA is pulling out all the stops.

Exterior and entryway of Boucheron’s Los Angeles Flagship
MajorsJul 02, 2025
Boucheron Looks to LA for First West Coast Flagship

Located on Rodeo Drive, the store’s design was inspired by Hollywood and Los Angeles culture.

Exterior of Marco Bicego Milan Flagship
MajorsJul 02, 2025
Marco Bicego Opens Milan Flagship

The new location continues the brand’s celebration of its 25th anniversary.

Chrono24 Time Is Our Thing campaign image
WatchesJul 02, 2025
Chrono24 Revamps Brand, Launches New Campaign

The online watch marketplace’s “Time Is Our Thing” campaign highlights the importance of time.

Bernadette Mack
SourcingJul 02, 2025
Bernadette Mack Joins Gem Legacy as Executive Director

She will oversee strategic planning, fundraising, industry partnerships, and the launch of the Gem Legacy Campus in Tanzania.

Counterfeit Pandora jewelry in bags and boxes
CrimeJul 02, 2025
Pandora, Amazon Partner to Uncover Counterfeit Jewelry Network

Working with Amazon’s Counterfeit Crimes Unit and law enforcement, Pandora helped to shut down a large-scale counterfeit network in China.

Cast Issa Rae
MajorsJul 01, 2025
Cast Closes Business, Plans for Relaunch

The jewelry company has closed its three California brick-and-mortar stores, as well as its online shop, for now.

Eve Goldberg, Matthew Denatale, Willie Lopez, Benjamin Goldberg
Events & AwardsJul 01, 2025
William Goldberg Diamonds, FIT Partner for Apprenticeship Program

The company is providing the opportunity for an FIT student to work alongside master diamond cutter Willie Lopez in its workshop.

Elie Hannoush
IndependentsJul 01, 2025
Elie Hannoush, Founder of Hannoush Jewelers, Dies at 73

He is remembered for his successful entrepreneurship, generosity, and dedication to his family.

Claire’s store
MajorsJul 01, 2025
Claire’s Is Looking for a Buyer, Report Says

The jewelry store chain has reportedly been struggling with costs related to tariffs as well as tough retail competition.

Mindi Mond Spike Earrings
TrendsJul 01, 2025
Amanda’s Style File: Red Hot Rubies

Welcome warm summer days with red hot rubies perfectly chosen as July’s birthstone.

The Story of Everything Campaign, Toadstool Mushroom and Cosmic Egg
CollectionsJun 30, 2025
State Property’s New Jewelry Tells ‘The Story of Everything’

Co-founders Afzal Imram and Lin Ruiyin brought their son’s story of a cosmic egg, toadstool, and railroad to life in their new collection.

Smart Age Solutions CEO Emmanuel Raheb
ColumnistsJun 30, 2025
The Smart Lab: Why Q3 Is the Secret Weapon For Holiday Jewelry Sales

The best time to prepare for the holiday season is right now, according to columnist Emmanuel Raheb.

Morgan Keefe
Events & AwardsJun 30, 2025
AGA Names Recipient of 2025 Gemological Education Scholarship

This year’s winner is Morgan Keefe, who is currently studying at GIA to be a gemologist.

The Jewelry Book
IndependentsJun 30, 2025
Melanie Grant’s New Book Explores 200 Years of Jewelry

“The Jewelry Book” comes out this September.

Gemist
TechnologyJun 27, 2025
Gemist Raises $6M in Funding to Scale Jewelry Tech Platform

The company is focused on modernizing the custom jewelry buying experience with e-commerce tools like product visualization and 3D styling.

Jeff Preolo, David Stout, Levi Higgs, David Benavides
IndependentsJun 27, 2025
David Webb Announces New Hires, Promotions

Following its recent acquisition, the storied brand has updated its leadership team and regional managers.

Blake Graham and Jessica Kohoutek
Events & AwardsJun 27, 2025
AGS, GIA Announce Beatrice Shipley Scholarship Winner

AGS also named the recipient of its “Women in Leadership” scholarship.

Buddha Mama Monstera Ring
CollectionsJun 27, 2025
Piece of the Week: Buddha Mama’s ‘Monstera’ Wrap Ring

The 20-karat yellow gold and diamond wrap ring is modeled after the Monstera plants in the garden of the brand’s Miami villa.

Cashier handing Rocksbox bag to customer
MajorsJun 26, 2025
Why Rocksbox Is Opening Stores As Signet Jewelers Downsizes

Rocksbox President Allison Vigil shared the retailer’s expansion plans, and her thoughts on opening stores in malls.

×

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