A Comparison of Diamonds and Colored Stones | GIA Knowledge Sessions Webinar Series

GIA Knowledge Sessions Webinar - recorded live on September 10, 2020.

Diamonds and colored stones are often considered to exist in entirely different realms in the gem and jewelry industry. This might partly be due to the fact that they are mined and brought to market so differently. Diamonds are primarily mined in large, industrial-scale operations, while colored stones such as rubies, sapphires and emeralds are typically produced by smaller-scale, often artisanal, operations. Their quality is also assessed very differently. Nonetheless, both diamonds and colored stones have helped scientists unlock secrets about Earth’s geology. Tune in as GIA Research Scientist Dr. Karen Smit and GIA Senior Manager of Research Dr. Aaron Palke reveal why these gems have more in common than you may have imagined.

Read more of Dr. Karen Smit's research:
https://www.gia.edu/gems-gemology/summer-2019-kimberlites-earths-diamond-delivery-system
https://www.gia.edu/gems-gemology/spring-2019-how-old-are-diamonds-are-they-forever
https://www.gia.edu/gems-gemology/winter-2018-how-do-diamonds-form-in-the-deep-earth

Read more of Dr. Aaron Palke's research:
https://www.gia.edu/gems-gemology/winter-2016-microworld-sphalerite-inclusions-namibian-demantoid
https://www.gia.edu/gems-gemology/fall-2015-microworld-glassy-melt-inclusions-sapphires-montana
https://www.gia.edu/gems-gemology/summer-2019-gemnews-rubies-from-rock-creek-montana

Questions answered by Dr. Evan Smith during the live webinar:

Q. What causes the red color in red Beryl?
A. It is thought to be caused by trace amounts of the element manganese in the crystal structure

Q. From which part of the mantle are diamonds extracted?
A. Most diamonds come from the thickest oldest parts of continents, from a depth of about 150 to 200 km. Rarely, diamonds come from deeper, perhaps as deep as 800 km or more. Diamonds are brought up from the mantle to Earth's surface in mantle-sourced volcanic eruptions, such as kimberlites.

Q. In the "Explained" Season 2 Episode 10 Diamonds -28 Nov 2019, was Dr. Karen Smit featured in that?
A. Indeed, she was featured in that episode. Good eye!

Q. What are the oldest and stable landforms names? Which continents or regions?
A. The oldest parts of continents, called cratons, can be seen in Figure 4 in the following article, where they are outlined in brown/gray colors: https://www.gia.edu/gems-gemology/wn13-advances-diamond-geology-shirey

Q. Please spell the name of the speaker for colored stones that Dr. Palke mentioned on YouTube.
A. Wim Vertriest. You can watch his presentation here: https://youtu.be/mDIRqF_02DE

Q. Mentioned in the presentation, the coloring elements are Cr/V but I heard that Fe is also an important element to determine origin in Emeralds. Does Fe also affect the color of an emerald?
A. Yes, in addition to chromium and vanadium, iron in an emerald crystal will affect the color. The presence or absence of each and their relative amounts determine the exact color of an emerald crystal.

Q. How to test the formation time of the diamond and its inclusions? How can we tell whether the diamond inclusion form at the same time with diamond, or crystallize after the diamond is formed?
A. Here is a great little writeup from Gems & Gemology that discusses diamond ages: https://www.gia.edu/gems-gemology/spring-2019-how-old-are-diamonds-are-they-forever

Q. How deep has man been able to drill into the crust so far?
A. The deepest drill hole is the "Kola Superdeep Borehole" and it is 12.2 km deep. Not very deep when you consider some of the depths discussed for diamond formation (150 km). Here is an article about the borehole from BBC: https://www.bbc.com/future/article/20190503-the-deepest-hole-we-have-ever-dug

Q. What does "ablate" mean?
A. Ablate means to zap the sample with a laser. The laser used to ablate the sample will break up some of the samples into individual atoms (or ions) so that they can be analyzed. The sample will have a little microscopic pit afterward, where some of the material has essentially been blasted away.

Q. Dr. Evan, super deep blue diamonds older than the oldest ones found in Ekati mines?
A. Not necessarily. Some blue type IIb diamonds might be younger, and some might be a similar age, as the oldest diamonds from Ekati. So far, we have not had the opportunity to determine the age of blue type IIb diamond directly, so we do not have a very good idea of how old they are.

Q. Measuring diamond age by radiometric dating the inclusion assumes that both the inclusion and the diamond formed at the same time. But isn't it possible that the inclusions were formed earlier and the diamond was formed later.
A. Yes, this it is possible. Here is a great little writeup from Gems & Gemology that discusses diamond ages in more detail: https://www.gia.edu/gems-gemology/spring-2019-how-old-are-diamonds-are-they-forever

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