Can inclusions or “flaws” in the gemstone tell you anything?

Inclusions contain important information about the gemstone and the natural history of our earth! Of course, most people that are familiar with diamonds would say, the more inclusions the diamond has the lower the quality. In grading gemstones, we are more forgiving in terms of clarity grading (here a brief article to explain it, https://www.gemsociety.org/article/colored-stone-grading-system/).

In this video, we would find out more about emeralds from Colombia! Those so called “flaws” that some people refer to are actually precious inclusions that tell so much about the gemstone! In the 4th stage of the mine to market story, a gemologist would examine the gemstone, test the physical properties and try to give the gemstone an identity (what gem it is), whether it has been treated and if possible where exactly or generally the gemstone is from (origin determination, one important mine for colombian emeralds is the Muzo mine http://www.muzo.co/en/millennial-legacy/muzo).

From an identification perspective, inclusions give you alot of information, from a valuation perspective it can add tremendous value if it does not affect the physical beauty of the gemstone, especially if the gemstone is from a renowned mine like Muzo for Colombian emeralds.

The moment you look at gemstones through a microscope, you will suddenly realise that there is a world of its own in the gemstone. Sometimes, these internal characteristics look to me like a snap shot of time, a snap shot of how the gemstone formed, a work of art and wonder.

You can watch this video to see some inclusions that are characteristic to Colombian Emeralds.

Featured in this video is the book called Photo Atlas by Dr E J Gubelin and Dr J I Koivula (you can get it at https://rubin-and-son.com/products_list.php?category_id=713). It contains photographs and explanation of many different inclusions in gemstones such as ruby, sapphire, emerald, alexandrite, fluorite, the list goes on.

Visit Far East Gemological Institute to start your gemology journey with our 1 day courses https://fareastgem.institute/courses/1-day-courses/

Gemstones that form in the Earth’s mantle

Only two gemstones form in the Earth’s mantle

diamonds can be found in the earth's mantle

Yellow Diamond from South Africa, a country known for its diamond mines. 

(Photo by Eric Nathan/Alamy, taken from National Geographic)

 

Together with diamonds, peridots are also found in the earth's mantleOlivine (Peridot) at the Natural History Museum, London.

(Photo by Aram Dulyan, via Wikimedia Commons, taken from International Gem Society)

 

Most gemstones form in the Earth’s crust. Only two gemstones form in the Earth’s mantle – the diamond and the peridot. These are gems that crystallise at extremely high temperatures.

 Fun fact: Diamonds may actually be the most plentiful crystals in the earth, but they just aren’t the easiest to reach

Diamonds are formed in the earth’s mantle.

Diamonds crystallise in very hot and fluid magma about 110 to 150 miles (117 to 241 kilometres) below the Earth’s surface. Because of the heat and fluidity, this magma is able to force a pathway up through the Earth’s crust at greater speeds and violence than other volcanic eruptions! These are called “kimberlite pipes”.

A simplified diagram of kimberlite pipe in earth's mantle and surface

  1. Magma pocket comes in contact with a weak area in crust.
  2. A quick explosion results, carrying diamond-bearing magma from the lower mantle to the surface. During the eruption, a cone builds on surface.
  3. The pipe eventually cools, leaving carrot shaped pipe.
  4. The cone quickly erodes away, leaving the diamond-bearing rocks where people can reach them.

(Diagram and description taken from International Gem Society)

 

If the rising of magma were any slower, the diamonds would likely not survive, as the changing temperatures and pressure would likely have caused them to vaporise or recrystallise as graphite.

This video shows a simple set up at The Gem Museum. It shows the formation and mining of diamonds in the world.

Peridot

Geologists believe that peridot first crystallises on rocks floating in the mantle about 20 to 25 miles (32 to 89 kilometres) below the Earth’s surface. Then an explosive eruption brings them near the Earth’s surface, and weathering and erosion brings them close enough to be mined and found.

 

Earth's mantle forms peridots
Peridot crystal from Pakistan (The Gem Museum)

 

peridot forms in earth's mantle
Peridot crystals from Lisu Village, North Myanmar. (The Gem Museum)

References / Further reading:

Gem formation – International Gem Society

Where did those gemstones come from – ThermoFisher Scientific

The Rock Cycle

The Rock Cycle

 

rock cycle diagram

All rocks are made up of minerals. The rock cycle explains the process.

A mineral is defined as a naturally occurring, crystalline solid of definite chemical composition and a characteristic crystal structure.

A rock is any naturally formed, nonliving, firm, and coherent aggregate mass of solid matter that constitutes part of a planet.

(Diagram and description taken from Idaho Museum of Natural History)

 

rock cycle diagram

(Diagram from Infohow.org)

 

Igneous rock

Igneous rock is formed when magma from the mantle rises up through the Earth’s crust, and cools and solidifies; or when lava on the Earth’s surface cools and solidifies. Igneous rocks are primarily created with heat.

Found in igneous rock: The quartzes (including amethyst, citrine and ametrine), the garnets, moonstone, apatite, diamond, spinel, tanzanite, tourmaline, topaz and zircon.

rock
Rock crystal (quartz) cut like diamonds.

 

Metamorphic rock

Metamorphic rock is formed when intense underground heat or pressure alters the existing atomic structures of minerals within rocks, and transforms them into other minerals. In essence, metamorphic rocks are created when heat and pressure change existing minerals into something new.

Found in Metamorphic rock: The beryls (emerald, morganite and aquamarine), jade, lapis lazuli, turquoise, spinel, ruby, sapphire, alexandrite, chrysoberyl and zircon.

0.77ct Ruby
0.77ct Ruby Madagascar
1.41ct Emerald
1.41ct Emerald Zambia
0.63ct Aquamarine
0.63ct Aquamarine
2.01ct Pink Sapphire
2.01ct Pink Sapphire
0.40ct Alexandrite
0.40ct Alexandrite
1.81ct Chrysoberyl Cat's Eye
1.81ct Chrysoberyl Cat’s Eye

Sedimentary rock

Sedimentary rock is formed when rock is worn down and the fragments are carried by water or the wind, and these sediments are finally compressed together over time.

Found in Sedimentary rock: Jasper, malachite, opal and zircon

 

The Gem Museum presents The Rock Cycle

rock cycle
The Rock Cycle set up at The Gem Musuem

 

The Gem Museum is set up to educate visitors on the story of “Mine to Market”. The very beginning of understanding gemstones is to learn about the rock cycle that is a very essential part of the formation of gemstones.

Come and visit us if you are in Singapore! We are opened Monday to Friday, 12pm to 5pm. Admission is free!

 

References / Further reading:

The Rock Cycle – 34 Kiwis

What is the Rock Cycle? – Idaho Museum of Natural History

Gem formation – International Gem Society

Where did those gemstones come from – ThermoFisher Scientific