Mineralogist Answers Gemstone Questions From Twitter | Tech Support

  • 9 months ago
Gabriela Farfan, the Smithsonian's curator of gems and minerals, answers the internet's burning questions about gemstones. Are all minerals crystals? How are diamonds cut? How do geodes form? Is the Hope Diamond actually cursed? This rock and mineral expert answers all these questions and more.

Director: Lisandro Perez-Rey
Director of Photography: Ben Finkel
Editor: Richard Trammell
Expert: Gabriela Farfan
Line Producer: Joseph Buscemi
Associate Producer: Brandon White
Production Manager: D. Eric Martinez
Production Coordinator: Fernando Davila
Casting Producer: Nick Sawyer
Camera Operator: Randy Feldman
Sound Mixer: David Campbell
Production Assistant: Brittany Barbour
Post Production Supervisor: Alexa Deutsch
Post Production Coordinator: Ian Bryant
Supervising Editor: Doug Larsen
Additional Editor: Paul Tael
Assistant Editor: Billy Ward
Transcript
00:00 I'm Gabriela Farfan, curator of gems and minerals at the Smithsonian.
00:04 Let's answer some questions from the internet.
00:06 This is Gem Support.
00:08 @Okoep asks, "I have a really dumb question that I'm too scared to ask in class.
00:18 What's the difference between rocks and minerals?"
00:20 There's nothing in a rock that is not a mineral.
00:23 Rocks are actually made up of minerals.
00:26 This is called granite.
00:28 If you look closely at this rock, you'll notice that it has grains of different colors.
00:33 These are individual crystals of different minerals.
00:37 Contained in this granite are the mineral quartz, the mineral feldspar,
00:42 and the mineral biotite and muscovite, which is also known as mica.
00:46 All minerals are crystals by definition.
00:49 In this case, this mineral is called quartz.
00:52 What is a gem?
00:53 A gemstone is a mineral crystal that has been cut and faceted by an artist.
01:00 So this would be the natural shape of a crystal,
01:02 and it can eventually be cut and polished into a gemstone.
01:06 @JebBlackwater asks, "Question.
01:09 What's the difference between rubies, emeralds, sapphires, etc?"
01:13 Rubies and sapphires are the same exact mineral.
01:16 The mineral is called corundum, and it is made up of aluminum and oxygen.
01:21 The only difference between ruby and sapphire is that the gem industry
01:25 designated the color red for rubies.
01:28 Every other color of the rainbow is called sapphire.
01:32 You also asked about emeralds.
01:34 Emerald is a variety of the mineral beryl.
01:37 Many minerals get their colors from different trace element impurities.
01:41 This one has chromium 3+ impurities on a very trace scale,
01:46 and this one has iron impurities to make it blue.
01:49 @SeamsterHeidi asks, "What's the most unusual gemstone you've ever heard of?
01:55 I need some inspiration."
01:56 I have a treat for you.
01:57 This is a mineral sodalite.
01:59 The variety name is called hackmanite,
02:01 and hackmanites are very special because they have a color property called tenobrescence,
02:07 which happens when we shine a UV light on it.
02:09 You'll see that the stones are now glowing an orange-yellow color.
02:14 We're going to charge them up a little bit.
02:16 Orange stone is from Mont-Saint-Hilaire, a very famous mine in Quebec,
02:22 and the yellow stone is from Afghanistan.
02:25 Okay, let's get the lights back on.
02:26 Now look at how the color of these stones has changed.
02:30 A tiny bit of sulfur gives it this color effect.
02:33 And now if we add some light to them, they'll go back to their original colorless versions.
02:38 So they're just reflecting all of the light back to us.
02:41 @leeperezray asks, "Where does the rock Dwayne Johnson rate on the Mohs scale?"
02:48 Well, Dwayne the Rock Johnson is off the scale because he's a cool human,
02:53 but his bones are actually made of bioapatite,
02:56 which is a mineral with a Mohs hardness of 5.
02:59 The Mohs hardness scale is a scale that we use to compare mineral hardness.
03:05 So when I say hardness, I'm actually referring to the scratchability of a mineral,
03:10 not how tough it is.
03:11 The mineral talc has a Mohs hardness scale of 1.
03:15 At the other extreme of the Mohs hardness scale, diamond is number 10.
03:20 The Mohs hardness scale is also a logarithmic scale,
03:24 which means that the difference between 1 and 2 on the scale is 10 times.
03:29 So diamond is 10 times 10 times 10 times 10 and so on, times harder than the mineral talc.
03:36 The reason why hardness is so important for gemstones that are used in jewelry
03:41 is that something like a diamond is very difficult to scratch.
03:44 So if you're wearing it every day in a ring,
03:47 it's much less likely to turn dull over time because it will not build up scratches.
03:52 Whereas diamonds are the hardest on the Mohs hardness scale, which means scratchability,
03:57 jade is the most difficult to break.
04:00 So it is the toughest mineral.
04:02 @petepeters21 asks, "If diamonds are the hardest substance in the world,
04:08 how do they cut diamonds?"
04:09 In order to cut a diamond, you need to use other diamonds.
04:13 They would have to take a rotating plate that we call a lap and cover it in diamond powder.
04:19 They'll start with a very coarse grit of powder,
04:23 and eventually they get to finer and finer grits to create the polished effect.
04:27 This is called the Kimberly diamond.
04:30 It's over 55 carats in weight,
04:32 and it originated from South Africa and was gifted to the Smithsonian in 2019.
04:38 This would be a rectangular or emerald cut.
04:41 You may also refer to it as a baguette cut.
04:44 And it's very special because most diamonds are cut in a round, brilliant shape,
04:49 which means that it's very good at disguising flaws.
04:53 Light comes into the diamond, bounces around the facets, and comes back out to your eye.
04:58 In this case, the light comes in, it bounces a little bit,
05:01 but you can see that there are no flaws in this diamond.
05:05 @sakasi asks, "How is a diamond's purity graded?"
05:09 The four Cs, which stands for its color, its clarity, its cut, and its carat weight.
05:16 There are many gemological institutes that can actually give your diamond a grade.
05:22 They'll look to see if it has any inclusions or impurities in the diamond,
05:27 such as another mineral that's stuck inside of the crystal,
05:31 or if it has any other flaws, like a crack.
05:34 Then they'll look at the color.
05:35 When grading colorless diamonds, people tend to prefer that there not be traces of yellow.
05:41 The yellow is due to small amounts of nitrogen
05:44 substituting into the carbon structure of the diamond crystal.
05:48 However, if there's a lot of nitrogen in the crystal,
05:51 it will turn more of a brilliant yellow color,
05:54 and that's actually considered a good thing.
05:56 We call this a fancy colored diamond.
05:58 They'll also look at how much it weighs, so the carat weight, which is a fifth of a gram.
06:03 They'll also then judge the cut of the stone.
06:06 So is it a round brilliant?
06:08 Is it a pear shape?
06:09 Is it a marquise cut, like an eye shape?
06:12 A marquise cut is an interesting cut that was more popular in the 80s.
06:17 @kxnu asks, "Do synthetic/cultured diamonds also last forever?"
06:22 Synthetic diamonds are chemically and crystallographically speaking
06:26 the same as naturally formed diamonds.
06:29 So they're also number 10 on the Mohs hardness scale.
06:32 They have the same optical properties, the same thermal properties,
06:35 and conductivity properties.
06:37 They were just not formed through geological processes.
06:40 They were formed in a laboratory.
06:41 Unfortunately for all of us, diamonds will not last forever
06:46 because diamonds are formed at very high pressures and temperatures.
06:50 So at Earth's surface conditions, they are not the stable form of carbon.
06:55 Graphite is the stable mineral at surface conditions.
06:59 So millions of years from now, maybe even longer,
07:02 your diamonds will turn into graphite.
07:04 @bloodiedroman asks, "Yo, they made Minecraft obsidian into a real thing?"
07:10 Sorry to break it to you, but obsidian was there first.
07:13 Here is a piece of obsidian.
07:15 An obsidian is actually natural volcanic glass.
07:20 So it's not a mineral because it does not have a crystal structure.
07:24 This obsidian glass has the same chemical composition to our granite.
07:29 They were magmas that formed underneath the surface of our planet.
07:33 But this one ended up nucleating and growing crystals,
07:36 whereas this one never had the chance.
07:40 Obsidian also has an anthropological connection
07:43 because it was used by prehistoric humans
07:47 because it breaks very easily and forms these conchoidal fractures,
07:51 which can be very sharp.
07:53 And they were used to make arrowheads and other knives.
07:56 @rocksbyk1 asks,
07:58 "What is the biggest difference between fool's gold and real gold?"
08:02 This is real gold.
08:03 Gold is a mineral, and it has this beautiful golden color.
08:07 In contrast, this is called fool's gold.
08:12 The proper name is pyrite, and it's composed of iron sulfide.
08:16 So it's not actually gold at all, but it also has this beautiful golden luster.
08:20 But if we hold them side by side,
08:22 you'll see that they're actually quite different in color.
08:25 They both have the same cubic structure for their crystal structure.
08:30 This one just happened to form more euhedral crystals,
08:34 more blocky, obvious crystals.
08:36 This one on an atomic scale would still be crystalline.
08:40 You just can't see the crystals with your naked eye.
08:42 @kayo_b_badaro asks,
08:44 "Do we theoretically know every mineral in the universe?"
08:47 We currently know of over 5,000 mineral species on our planet today.
08:53 As for the whole universe, I cannot say.
08:55 But theoretically speaking, we know that the combinations of different elements
08:59 in the periodic table could account for approximately 9,000.
09:03 So we still have a ways to go to keep finding those minerals.
09:06 We're going to need some more mineralogists in the future to help us look for them.
09:10 @benking01 asks,
09:12 "Where do the minerals in your mobile phone come from?"
09:15 There are approximately 65 elements that are necessary to make your cell phone run.
09:20 Many of them are considered to be rare earth elements
09:23 that oftentimes come in what we call critical minerals.
09:26 For example, one of these minerals would be called spodumene.
09:30 And this mineral happens to have a lot of lithium in it.
09:33 And lithium is going to be very important for those lithium ion batteries.
09:38 We mine spodumene from rocks called pegmatites.
09:42 And pegmatites are really, really great at concentrating
09:46 what we call these incompatible elements.
09:48 These are elements that are either too small, like lithium,
09:51 or too big, like uranium, that they don't like to fit in your average crystal structures.
09:57 Pegmatite deposits occur across the globe,
10:00 but they tend to be concentrated in places like Brazil.
10:03 We even have some pegmatites here in the United States, up in Maine or in California.
10:08 @theinspiraz asks, "What is the most cursed diamond?"
10:13 Historically, people loved the idea of attaching a curse or a good story to a famous diamond.
10:20 And what more famous diamond than the Hope Diamond,
10:22 which resides here at our National Museum of Natural History.
10:26 In the early 1900s, the Hope Diamond was bought and sold many times,
10:31 and all of its owners kept losing their money in having to sell this diamond.
10:35 And its last private owner, Evelyn Walsh McLean,
10:38 had a rather tragic life that befell her family and herself.
10:42 So this idea of the curse just kept building and building with the Hope Diamond.
10:46 But today, when we think about the Hope Diamond, we actually think of it as a blessing,
10:50 because it has become the cornerstone of our National Gem Collection.
10:54 @PhilBrown62 asks, "How do crystals form?"
10:58 Different minerals require different temperature or pressure conditions
11:03 in order to build their crystals.
11:05 They also need some kind of fluid in order for those necessary ingredients to get to the right place.
11:10 Crystals are formed of atoms, and so if you have consistent ingredients,
11:15 in the case of this amethyst, which is a variety of quartz,
11:18 the ingredients would be silicon and oxygen.
11:20 The silicon and oxygen atoms will arrange themselves in a repeating, specific pattern.
11:26 In this case, it will make a hexagonal crystal system.
11:29 And if you keep adding atoms to this tessellation,
11:34 you will eventually end up with a crystal that you can see with the naked eye.
11:37 @LauraOpper asks, "Are pearls considered to be minerals, since their origin is organic?"
11:43 Pearls are technically not minerals, because they are formed through organic processes.
11:49 And part of the definition of a mineral is that it has to form inorganically.
11:53 However, I'm actually a biomineralogist,
11:56 so I do study minerals that are formed through biological processes.
12:01 And in the case of pearls, what we're looking at is the mineral aragonite, or calcium carbonate.
12:06 So what happens is that the organism, in this case a pearl oyster,
12:11 naturally forms this layer of nacre, or mother of pearl, inside of its shell.
12:17 And if a piece of debris gets stuck inside of its organism as it's living,
12:21 it becomes irritated, and it tries to cover that with the same nacre that we call a pearl.
12:27 Another example of a biomineral would be your bones.
12:31 You are, in fact, a biomineralizing organism, where your bones are made up of bioapatite.
12:36 Apatite is calcium phosphate, and it's also formed through geological processes.
12:41 @bracer788 asks, "What does gemmy mean?"
12:45 We say that something is gemmy when someone could potentially cut a gemstone out of it.
12:51 For example, this crystal of beryl, also known as the variety emerald, is very beautiful.
12:57 It's rather transparent.
12:59 This gemstone could potentially be cut out of a crystal like this because the crystal is gemmy.
13:06 In contrast, this crystal is relatively opaque,
13:09 which means it would be very difficult to cut a gemstone out of this crystal.
13:14 @emmatheresaj asks, "My friend has a moonstone (orthoclase ring)
13:19 that the jeweler told her she can't get wet.
13:22 Is this true?
13:22 What's behind that crystallographically/geochemically, or is this a myth?"
13:26 Moonstone looks something like this.
13:28 You can get it wet, it's not going to be harmed whatsoever.
13:32 Now, the jeweler might have been confused with a different thing, which we call opal.
13:38 Opals look something like this, and they are also commonly used in jewelry,
13:42 but they're not technically minerals.
13:44 Opals are mineraloids, which are almost the same as minerals,
13:48 but they don't have a crystal structure.
13:50 Instead, opals are composed of tiny, tiny spheres made out of silica,
13:55 and these spheres are packed together.
13:57 This means that opals are very porous, and they can easily absorb water.
14:02 So if you're going to do your dishes, maybe take your opal ring off first.
14:06 @tiffysniffs asks, "How are geodes formed, and why are they so cool?"
14:11 Well, I agree that geodes are very cool.
14:14 If you were to walk around in Utah and pick up a rock that looks something like this,
14:19 break it open, you might find that it's hollow inside, and that it formed a geode.
14:25 So geodes form when you have an open cavity,
14:28 and this allows crystals to grow inside of the space.
14:33 This one is likely filled with the mineral called quartz, or silicon dioxide.
14:37 This would be your most common geode that you would find.
14:41 If you're going to crack open geodes, make sure that you wear your safety glasses.
14:45 Safety first.
14:47 @shelbybylynn11 asks, "Why does turquoise jewelry have to be so expensive?"
14:53 Because the gemstones that they're made from are quite rare.
14:57 It's very difficult, first of all, for the Earth to create these amazing minerals,
15:02 and to form examples of them that are going to be large enough,
15:05 pretty enough, in order for someone to want to make jewelry out of them.
15:09 The next part would be someone has to mine that stone.
15:12 So a miner would go to a mine, such as one in Arizona, find that turquoise,
15:16 then it has to go to a lapidary, which is the person that actually cuts the stones
15:22 into a cabochon, which is a stone that's polished on top and usually flat on the bottom,
15:28 so it makes a dome shape.
15:30 And finally, you need a jeweler that's going to take that gemstone
15:33 and mount it into a piece of jewelry.
15:35 Now, the metal that is used to mount that piece of jewelry can be quite expensive in and of itself,
15:41 especially if it's something like gold or platinum.
15:44 So together, you form this rather expensive piece of jewelry.
15:48 @linostrack asks, "Where do rubies even come from?"
15:51 It turns out that rubies, or the mineral corundum, can be found all around the world.
15:56 If you were interested in finding rubies in the United States,
15:59 you could even go to North Carolina to ruby mines.
16:02 However, the most precious rubies, the most sought-after rubies, are from Burma.
16:07 There is an area of Mogok, Burma, that has a huge city made up of many,
16:13 many thousands of people where their entire job is to find rubies in a mountain of marble.
16:19 @tailsandkitty asks, "What are 'blood diamonds'?"
16:22 Unfortunately, minerals and gemstones often hold a lot of value per volume,
16:29 which means they're very small, but they're very, very expensive.
16:32 And thus, they have been embroiled in conflicts and used to trade for weapons,
16:38 and oftentimes can be directly linked to conflicts and death.
16:42 Ethical sourcing is very important.
16:44 Currently, there is a process called the Kimberley process,
16:47 which can trace the origins of diamond crystals before they get cut and sold into jewelry.
16:54 So if a diamond comes into the United States without the proper certification
16:59 from the Kimberley Committee, they get confiscated by TSA,
17:03 and they're actually brought here to the Smithsonian's National Museum of Natural History
17:08 so that they don't get traded out illegally.
17:10 @degenixplay asks, "How do you find your gems?"
17:14 As the curator of gems and minerals, myself and my team go out and scout
17:19 for new minerals that have appeared on the market.
17:21 Recently, we acquired a crystal of the mineral called saffirine, not sapphire,
17:27 and it was one of my favorite acquisitions because it happens to be
17:30 the largest crystal of saffirine in the world, and it came from a mine in Madagascar.
17:35 So those are all the questions we have today.
17:37 Thanks for watching Gem and Mineral Support.
17:40 [MUSIC PLAYING]

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