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LuxeSci Show Notes: S1E14: Emeralds

Hello again.  Welcome back to LuxeSci - a podcast to re-ignite your wonder by exploring the science behind luxury items.  It’s been a little bit so I thought we should re-introduce ourselves.  I’m Dr Lex, PhD, I have a PhD in microbiology and immunology and a Masters in Public Health Microbiology. I’ve worked at the NIH and the CDC and currently am in the clinical trial world.   I’m joined by my co-host Dr. Dimos, Dimos has a PhD in electrical engineering, has worked on drives for hybrid vehicles, invented his own solar inverter and currently works in the rocket business.  Collectively, we bring a few decades of experience in scientific research.  We are also both incredibly curious people and often wonder about things and find ourselves on-line to look up one thing or another. So this episode we’re exploring the epitome of green gemstones, emerald

Dimos - what is something you wondered about emeralds before this episode

Me - I wondered how emeralds are different from other gemstones

So originally I thought we were doing sapphires for this episode and had posted on our social media about it and even started my notes and then Dimos reminded me that per our schedule, we’re doing emeralds.  That makes sense because emeralds are the birthstone for May (lucky Maybies).  I don’t have any personal anecdotes or experience with emeralds but they are beautiful.

So here’s what two non-geologist PhDs found out about emeralds


  • Dimos


  • So i have something a little different this time.  Usually, I go to Pubmed to look at how our luxury item of choice is used in biomedical research.  (this is where I feel the most comfortable scientifically)

  • This time, that didn’t really work.  Apparently there aren’t a lot of biomedical applications for emeralds. It would be interesting to delve into why that is…but we have a podcast to do

  • What I did find is from the Gemological Institute of America.  According to their website, the GIA was established in 1931to provide knowledge,standards, and education in gems and jewelry.  The work with diamonds, colored stones and pearls and also do research

  • I follow them on Instagram (highly recommend, a perfect combo of pretty, shiny things and science) and they recently posted about some fossilized shells that they received for analysis

  • Their Hong Kong lab received 11 fossilized shells that were encased in..//emerald!

  • The GIA lab put the fossils under a microscope and saw “numerous small light green to green anhedral emerald crystals contained very fine fluid inclusions associated with well-formed brassy pyrite grains”  (As a reminder, inclusions are any material that is trapped in the mineral during formation ) These inclusions are indicative of Columbian emeralds. 

  • The lab performed X-ray radiography (which is when an X-ray beamis passed through the specimen.  The X-rays are absorbed or scattered by the internal structure of the specimen, in this case the fossil. The remaining x-rays are transmitted to the detector, which makes a pattern that can be visualized, like an X-ray at the doctor.) and found the spiral pattern of the shell but emerald crystals evenly distributed, which indicated that the mineral had completely replaced the shell material. 

  • So how does this happen?

  • The GIA worked with the Laboratoire Français de Gemmologie (LFG) in Paris to submit other shell fossils to X-ray tomography analysis, which is also based on the differential absorption of X-rays by different types of specimens.  You may know it as a CT scan as it produces cross-sectional images

  • Origin of the word tomography is from Greek. Tomos = slice and graphy = drawing

  • They found no remains of the original shell and indications that the crystals had grown from the solid parts of the animal out to the shell and inside to the hallow parts.  The scientists hypothesized the the shell was replaced gradually by many small crystals that later coalesced into a single crystal by a process known as Ostwald ripening

  • Ostwald ripening: Dissolution of small crystals and the redeposition of the dissolved species on the surfaces of larger crystals 

  • This thermodynamically-driven spontaneous process occurs because larger particles are more energetically favored than smaller particles

  • One example of Ostwald ripening is the re-crystallization of water within ice cream which gives old ice cream a gritty, crunchy texture. Larger ice crystals grow at the expense of smaller ones within the ice cream, creating a coarser texture.[14]

  • Another gastronomical example is the ouzo effect, where the droplets in the cloudy microemulsion grow by Ostwald ripening.

  • Now this only happens with anise-flavored alcohols

  • Interesting the emulsion that forms is highly stable

  • So this happens when a highly hydrophobic (afraid of water) oil such as anethole (flavoring) is dissolved in a water-miscible solvent (ethanol)(essentially a solvent that can mix fully with water). 

  • Normally this isn’t stable because the oil droplets coalesce

  • In Ouzo the droplet coalesence is slowed and using microscopy scientists have shown that the droplets grow by Ostwald ripening and not coalescence

  • I’ll stop it there in case we want to do an episode on the science of ouzo one day


  • X-ray tomography - CT scan

  • Ostwald ripening - dissolution of small crystals and the redeposition on surfaces of larger crystals

Fun fact

  • Why does the emulsion of ouzo and water not disperse quickly - Ostwald ripening



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