Latest / PlanetGeo: The Geology Podcast / The Silicates. Geology 101: Minerals Part 2

Transcript

The Silicates. Geology 101: Minerals Part 2 · PlanetGeo: The Geology Podcast

• 0:01
  SPEAKER_00: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:15
  SPEAKER_00: Check, check, check.
• 0:17
  SPEAKER_00: Hey folks, part two of our Camp Geo Intro to Minerals section.
• 0:22
  SPEAKER_00: We are taking a quick break while we're working on a bunch of other projects that we're excited to announce, that we're excited to announce in the future.
• 0:29
  SPEAKER_00: But at the same time, many of the podcast platforms now allow chapter images in uh kind of uh half of what you get on our Camp Geo Mobile app.
• 0:37
  SPEAKER_00: So we're dumping a bunch of content from the Camp Geo Mobile app into the podcast feed for the next couple weeks here.
• 0:42
  SPEAKER_00: You can follow us on all the social medias.
• 0:43
  SPEAKER_00: We're at Planet GeoCast.
• 0:45
  SPEAKER_00: Shoot us an email.
• 0:45
  SPEAKER_00: There's a contact us link on our website, planetgeocast.com, and download our Camp Geo Mobile app.
• 0:51
  SPEAKER_00: First link in your show notes.
• 0:53
  SPEAKER_00: Check it out.
• 0:53
  SPEAKER_00: Let us know what you think.
• 0:56
  SPEAKER_00: Chris, you ready to rock?
• 0:57
  SPEAKER_00: I am ready to go.
• 0:58
  SPEAKER_00: You ready?
• 0:58
  SPEAKER_00: Let's do it.
• 0:59
  SPEAKER_00: Hey, this is episode two.
• 1:00
  SPEAKER_00: This is episode number two.
• 1:02
  SPEAKER_00: And the title of this is What Elements Make Up the Earth and the Silicate Structures.
• 1:06
  SPEAKER_00: But before we get into that, let's review real quick.
• 1:08
  SPEAKER_00: Last episode, we covered basics of mineral chemistry.
• 1:11
  SPEAKER_00: We talked about the five things that define what a mineral is.
• 1:15
  SPEAKER_00: We talked about ionic and covalent bonding, the difference between them.
• 1:19
  SPEAKER_00: We kind of briefly touched on a review of what an atom looks like, electrons in the outer shell, protons, neutrons in the nucleus.
• 1:27
  SPEAKER_00: And then we wrapped it up by covering an analogy of how elements stack together to make minerals and how they most efficiently do that given a chemical composition.
• 1:39
  SPEAKER_00: So where are we going here, Chris?
• 1:41
  SPEAKER_02: Yeah.
• 1:41
  SPEAKER_02: So today what we're going to cover, we're going to talk about the atoms that make up the earth.
• 1:46
  SPEAKER_02: And the earth has different layers.
• 1:48
  SPEAKER_02: We're going to talk about these layers and then chemically, what's in these layers?
• 1:52
  SPEAKER_02: What are the dominant elements that are present?
• 1:55
  SPEAKER_02: And then from there, we're going to use that to jump into the silicate structures.
• 2:00
  SPEAKER_02: And this is this is new.
• 2:02
  SPEAKER_02: The students have not been exposed to this probably at this level yet.
• 2:05
  SPEAKER_02: So this is going to be new material.
• 2:06
  SPEAKER_02: We're going to talk about the most important mineral group and why it's the most important mineral group.
• 2:12
  SPEAKER_00: That's today.
• 2:13
  SPEAKER_00: So the earth is layered, it is what we call differentiated.
• 2:17
  SPEAKER_00: We have different chemical compositions as we go deeper down into the crust.
• 2:21
  SPEAKER_00: And one typical analogy here is an apple.
• 2:25
  SPEAKER_00: And the apple has an outer layer of the skin, and then it has a big meaty part, and then it has the stuff in the middle with the seeds in it.
• 2:33
  SPEAKER_00: And that's kind of similar to the earth.
• 2:35
  SPEAKER_02: So the first image that you have in your stack for today's episode is an image that shows the the three basic layers of the earth.
• 2:45
  SPEAKER_02: It's the crust, the mantle, and the core.
• 2:48
  SPEAKER_02: And we're going to talk about those briefly here, and then what elements are in each of these differentiated layers of the earth.
• 2:57
  SPEAKER_02: So, Jesse, let's go.
• 2:59
  SPEAKER_02: Let's start, let's start talking about it.
• 3:00
  SPEAKER_00: The structure of the earth.
• 3:02
  SPEAKER_00: Yeah, the structure of the earth.
• 3:03
  SPEAKER_00: So that image shows it perfectly.
• 3:05
  SPEAKER_00: There's three major ones.
• 3:06
  SPEAKER_00: The crust is the outermost one.
• 3:08
  SPEAKER_00: Think of it like the skin of an apple.
• 3:10
  SPEAKER_00: The crust is actually very thin compared to the full thickness of the earth.
• 3:14
  SPEAKER_00: As we get in past the crust, we get into the mantle, which is a different chemical composition.
• 3:19
  SPEAKER_00: So the difference between the crust and the mantle is a chemical difference.
• 3:23
  SPEAKER_00: And then we get into the core, and the core has two layers in it, but it is again a chemical difference between the mantle and the crust.
• 3:30
  SPEAKER_00: These are all distinct chemical layers.
• 3:32
  SPEAKER_00: There's two layers within the core, but they're kind of the same chemistry.
• 3:36
  SPEAKER_02: Yes.
• 3:36
  SPEAKER_02: So are you saying that then the earth looks like an apple in terms of the way it's layered together?
• 3:41
  SPEAKER_02: Yeah, I think it's an okay analogy.
• 3:43
  SPEAKER_00: The skin of the apple is the crust, and then you have the meat of it in the middle, and then you get into the seeds and stuff, the junk in the core that you never really eat.
• 3:50
  SPEAKER_02: Yeah, I don't know, Jess.
• 3:51
  SPEAKER_02: I I'm not like the the core part of it falls apart because the core of an apple is not really I don't like it.
• 3:58
  SPEAKER_02: You're not really convinced by my analogy, huh?
• 4:01
  SPEAKER_02: No, I'm not.
• 4:02
  SPEAKER_02: I think a peanut MM is a much better analogy.
• 4:04
  SPEAKER_02: Plus, uh yeah, I think a peanut MM, right?
• 4:07
  SPEAKER_02: That's a tastier analogy.
• 4:09
  SPEAKER_02: Cold crunchy shell.
• 4:10
  SPEAKER_02: Okay.
• 4:11
  SPEAKER_02: Then below that, this milk chocolate that is like the mantle of the earth, right?
• 4:15
  SPEAKER_02: And then you have the the peanut part of the peanut MM, which represents I think pretty well the core of the earth.
• 4:23
  SPEAKER_02: Now, like you said though, it's not perfect because you know the core has two layers.
• 4:27
  SPEAKER_02: It's got a liquid outer core and a solid inner core.
• 4:30
  SPEAKER_02: So maybe if we took this would be make it perfect.
• 4:33
  SPEAKER_02: If we took a peanut MM and injected like a caramel, uh soft caramel fluid around the peanut part, then we have the structure of the earth.
• 4:44
  SPEAKER_02: That that works about perfectly.
• 4:47
  SPEAKER_00: Okay.
• 4:47
  SPEAKER_00: So are you a little bit hungry right now, Chris?
• 4:49
  SPEAKER_00: Is that where we're going with the analogy?
• 4:52
  SPEAKER_00: I figured it'd be.
• 4:53
  SPEAKER_00: So, okay, we've got our chocolate infused bean and MM.
• 4:56
  SPEAKER_00: Perfect.
• 4:57
  SPEAKER_00: That's a better analogy than Apple.
• 4:58
  SPEAKER_00: The core, uh, the core is a lot better there.
• 5:00
  SPEAKER_00: But the three main chemical differences are core, mantle, and crust.
• 5:04
  SPEAKER_00: And there's chemical differences, either chemical layers, they're also physical layers as well, but there are big chemical differences between these things that we're gonna kind of give an overview of right now.
• 5:14
  SPEAKER_00: But these layers will be incredibly important for the entire rest of this course.
• 5:19
  SPEAKER_02: What about if we start at the inside of the earth and work our way out to the crust?
• 5:22
  SPEAKER_02: Because that's really we're gonna deal with the crustal composition mostly today.
• 5:26
  SPEAKER_02: So we'll end with that.
• 5:27
  SPEAKER_02: All right.
• 5:28
  SPEAKER_02: Yep.
• 5:28
  SPEAKER_02: So the core.
• 5:30
  SPEAKER_02: The core is almost well, let me say this.
• 5:34
  SPEAKER_02: The core is mostly made of iron.
• 5:37
  SPEAKER_02: It has some other chemical components to it, but the reason why we have this stark, you know, boundary right there, compositional boundary, is because it is mostly made of iron.
• 5:49
  SPEAKER_02: All right.
• 5:49
  SPEAKER_02: Now the layer around that is the mantle.
• 5:52
  SPEAKER_02: Now we have a different chemical composition of this, and this is a big difference.
• 5:56
  SPEAKER_02: All right.
• 5:57
  SPEAKER_02: The core was almost 80% iron.
• 5:59
  SPEAKER_02: Now the mantle is made up mostly of silicon and oxygen.
• 6:04
  SPEAKER_02: In terms of the the abundance of the atoms, 20% of the atoms are silicon, about 45% of them are oxygen, and then magnesium has about 20% of the atoms as well.
• 6:17
  SPEAKER_00: Right.
• 6:18
  SPEAKER_00: And this is a huge difference.
• 6:19
  SPEAKER_00: There's very little iron.
• 6:21
  SPEAKER_00: Well, there's still some 5%, but not nearly as much as the core.
• 6:25
  SPEAKER_00: And there's a big bonding difference between these things.
• 6:27
  SPEAKER_00: The iron core is mostly metal, so it has metallic bonds.
• 6:30
  SPEAKER_00: The silicate, what we call silicate mantle, it's composed mostly of silica and oxygen with some magnesium in there.
• 6:37
  SPEAKER_00: It has a completely different structural composition.
• 6:40
  SPEAKER_00: So that is what we call silicate, is the mantle.
• 6:42
  SPEAKER_00: And then we move to the crust, which is what we live on, what we interact with mostly.
• 6:47
  SPEAKER_00: We can see parts of the mantle exposed on Earth in different areas, but we're dealing with the crust mostly.
• 6:53
  SPEAKER_02: When I ask my students, before we talk about this at all, what do you think the most abundant element in the crust is?
• 7:02
  SPEAKER_02: Do you know what they almost always say?
• 7:04
  SPEAKER_02: Um, I'll bet they say aluminum.
• 7:08
  SPEAKER_02: No, they don't.
• 7:09
  SPEAKER_02: They say carbon.
• 7:10
  SPEAKER_02: Oh, yes, actually.
• 7:11
  SPEAKER_02: They almost always say carbon.
• 7:13
  SPEAKER_00: I got that this year too.
• 7:14
  SPEAKER_00: I asked that question, and carbon was a very popular one.
• 7:16
  SPEAKER_00: Yep, for sure.
• 7:18
  SPEAKER_02: Carbon doesn't even make the top eight list.
• 7:20
  SPEAKER_02: I get the answer.
• 7:21
  SPEAKER_02: I I understand where they're coming from.
• 7:23
  SPEAKER_02: You know, because I think they know that, you know, all of life is carbon-based, and so that makes sense, but it's just it doesn't make the list.
• 7:31
  SPEAKER_02: The most, the three most abundant elements are silicon, oxygen, and aluminum.
• 7:37
  SPEAKER_00: That's right.
• 7:38
  SPEAKER_00: And carbon doesn't make the list because life is on top, but the as just on top of the crust, the crust is actually really thick.
• 7:45
  SPEAKER_00: The crust is anywhere between seven to fifty or seventy kilometers thick, depending on where you are on the earth.
• 7:50
  SPEAKER_00: So the crust, there's a huge amount of rock in the crust.
• 7:53
  SPEAKER_00: So, as you said, silica, oxygen, and aluminum are the main elements in the crust.
• 7:58
  SPEAKER_02: I understand what you said.
• 7:59
  SPEAKER_02: It's thick from a human perspective, but in terms of a scale of the earth, the crust is very, very thin.
• 8:05
  SPEAKER_02: Okay, if you think of a bowling ball, wrap the bowling ball with tissue paper, that translucent kind of tissue paper, on that scale, that would be about the approximate thickness of the crust.
• 8:17
  SPEAKER_00: That is exactly right.
• 8:18
  SPEAKER_00: So the crust is only a few to a few tens of kilometers thick.
• 8:21
  SPEAKER_00: The mantle goes from about on average 40 kilometers to about 2,900 kilometers deep.
• 8:27
  SPEAKER_00: And then we have the core, which goes from about 2,900 all the way to about 5,200 kilometers deep.
• 8:33
  SPEAKER_00: So the core and the mantle make up a much bigger proportion of the earth than the crust does.
• 8:37
  SPEAKER_00: So Chris, how do the how do these elements, we've talked about silica, oxygen, aluminum, magnesium, these are big in the mantle and crust, how do they arrange themselves in the quote unquote silicate part of the earth, this mantle and crust part?
• 8:52
  SPEAKER_02: Right.
• 8:52
  SPEAKER_02: Um so the two most abundant elements in the crust are easily silicon and oxygen.
• 8:59
  SPEAKER_02: And then when you look at the two most common minerals that exist in the crust, it's gonna in it has to involve those two elements more than anything else.
• 9:10
  SPEAKER_02: And quartz and feldspar are the two most common minerals in the crust, and they are predominantly made up of silicon and oxygen.
• 9:18
  SPEAKER_02: So how do these atoms arrange themselves?
• 9:22
  SPEAKER_00: Yeah, because silicon and oxygen are so prevalent, the minerals that make up the crust and the mantle will have to be dominated by silicon and oxygen.
• 9:31
  SPEAKER_00: So the way that silica and oxygen arrange themselves really defines how most of the crust and mantle arranges itself.
• 9:37
  SPEAKER_00: And the minerals present in the crust and mantle are mostly all silica and oxygen based.
• 9:44
  SPEAKER_00: There are other metal elements sprinkled in there.
• 9:46
  SPEAKER_00: But we have to think about how silica and oxygen arrange themselves first.
• 9:49
  SPEAKER_00: And that gives us the biggest group of minerals.
• 9:52
  SPEAKER_00: The most prevalent, the most popular, the most common group of minerals is what's called the silicate minerals, which are all based on the way that silica and oxygen arrange themselves together.
• 10:03
  SPEAKER_00: And that is what's called the silica tetrahedron, Chris.
• 10:06
  SPEAKER_00: So what is the silica tetrahedron?
• 10:08
  SPEAKER_00: Besides being so fundamental, what is it?
• 10:09
  SPEAKER_00: Let's let's visualize it.
• 10:11
  SPEAKER_02: I want to start, though, before we dive into the structures, I want to start with like these principles that kind of surround this, because I think it's really an interesting story.
• 10:20
  SPEAKER_02: There are three basic things that go into the building of a silicate structure.
• 10:25
  SPEAKER_02: Okay.
• 10:25
  SPEAKER_02: The first thing is that silicon atoms surround themselves with four oxygens.
• 10:31
  SPEAKER_02: And that goes back to our prior lecture, right?
• 10:33
  SPEAKER_02: Why do they do that?
• 10:34
  SPEAKER_02: Because that's the best way to stack silicon and oxygen together.
• 10:39
  SPEAKER_02: It's an SIO4 structure.
• 10:42
  SPEAKER_00: So if we go back to that analogy, tennis balls and marbles we used last time, it's like giving you what, three times the tennis balls as marbles that you give.
• 10:50
  SPEAKER_00: So we have, you know, a ratio of three to one here that I'm giving you.
• 10:54
  SPEAKER_00: And the best way to stack that is this one to four relationship, right?
• 10:58
  SPEAKER_02: Yeah.
• 10:59
  SPEAKER_02: So the second principle is that you have it forms this what we call the silicate tetrahedron.
• 11:04
  SPEAKER_02: Tetra means four.
• 11:06
  SPEAKER_02: Okay.
• 11:06
  SPEAKER_02: The silicate tetrahedron, it looks like a pyramid.
• 11:10
  SPEAKER_02: Imagine a pyramid in front of you.
• 11:12
  SPEAKER_02: Okay.
• 11:13
  SPEAKER_02: And in the middle of the pyramid is going to be the silicon atom.
• 11:16
  unknown: Okay.
• 11:17
  SPEAKER_02: And then the four points that make the pyramid are going to be the oxygen atoms.
• 11:23
  SPEAKER_02: And so if you look at the second slide in your image stack, this image shows that perfectly where the tips of the pyramid are the oxygen atoms and they're connected to the center, which is the silicon atom.
• 11:37
  SPEAKER_02: Okay.
• 11:38
  SPEAKER_02: I want to just real quick wrap this up, Jesse.
• 11:40
  SPEAKER_02: The third principle here, and this is what is really interesting, I think, is that in terms of the number of atoms that exist in the crust, oxygen is 63%.
• 11:51
  SPEAKER_02: Silicon is 21%, which means there are three times more oxygens available than there are silicon atoms.
• 11:58
  SPEAKER_02: That presents a problem, right, Jesse?
• 12:00
  SPEAKER_02: What's the problem with that?
• 12:01
  SPEAKER_00: Yeah, the problem is that you just described this pyramid, and your image number two in the stack shows this pyramid where you have one to four.
• 12:08
  SPEAKER_00: So that ratio is a little bit off.
• 12:10
  SPEAKER_00: 63% to 21% is three to one.
• 12:13
  SPEAKER_00: This tetrahedron really has a four to one ratio.
• 12:16
  SPEAKER_00: So we're either missing some oxygen somewhere or our bonding environment is different.
• 12:21
  SPEAKER_02: Yeah, that's exactly right.
• 12:23
  SPEAKER_02: And this goes back to the bonding that we talked about in the prior episode, the covalent bonding.
• 12:28
  SPEAKER_02: These are going to share oxygen atoms so that the O4 can be achieved.
• 12:37
  SPEAKER_00: It brings the ratio down.
• 12:39
  SPEAKER_00: So this means that we're going to put those pyramids together so that they are sharing corners, so that these silica atoms sitting in the middle will be sharing oxygens between them.
• 12:49
  SPEAKER_00: And this is the basis for a group of minerals which are really important, the silicate minerals, which are all based on this silica tetrahedron.
• 12:56
  SPEAKER_00: And the ways that we stack these silica tetrahedrons together defines how these minerals behave.
• 13:02
  SPEAKER_00: But they're all fundamentally based on the silica tetrahedron, these pyramids, that image number two.
• 13:07
  SPEAKER_00: That's the building block for silicate minerals.
• 13:10
  SPEAKER_00: So we're going to go through the five different silicate structures.
• 13:13
  SPEAKER_00: And there's five of them in here, and there are five images in your stack that show these.
• 13:17
  SPEAKER_00: So we're going to go through those right now, Chris.
• 13:19
  SPEAKER_02: I want to just real quick mention one thing.
• 13:22
  SPEAKER_02: You know, you said that this is easily because silicon and oxygen are the most abundant elements in the crust, that makes then the this group of minerals the most important and a most abundant group of minerals that exist in the crust.
• 13:34
  SPEAKER_02: You know, in my classroom, I probably have 3,000 different mineral samples on display.
• 13:40
  SPEAKER_02: You know, my school built me great display cases and all that.
• 13:43
  SPEAKER_02: The vast majority of the minerals that I have on display are silicate minerals because they're just the most common minerals that exist.
• 13:53
  SPEAKER_00: Yeah.
• 13:54
  SPEAKER_02: Here we go.
• 13:55
  SPEAKER_02: Let's go through the five.
• 13:56
  SPEAKER_02: Well, let's start simple and work our way to the most complicated, right?
• 13:58
  SPEAKER_02: That makes sense?
• 13:59
  SPEAKER_02: Totally.
• 14:00
  SPEAKER_02: So the first of the five silicate structures is called the single tetrahedron.
• 14:04
  SPEAKER_02: Okay.
• 14:04
  SPEAKER_02: This is again image two in your stack.
• 14:07
  SPEAKER_02: And this is just simply SiO4.
• 14:11
  SPEAKER_02: But Jesse, that forms a negatively charged ion, right?
• 14:17
  SPEAKER_00: That's exactly right.
• 14:18
  SPEAKER_00: And this is very important for considering how we structure these pyramids together, because Si, silicon, likes to give away four electrons.
• 14:27
  SPEAKER_00: That's its most stable bonding state.
• 14:28
  SPEAKER_00: So it likes to be in a plus four charge state.
• 14:31
  SPEAKER_00: Oxygen likes to have two electrons.
• 14:33
  SPEAKER_00: It likes to get two electrons.
• 14:35
  SPEAKER_00: It likes to be in a minus two charge state.
• 14:38
  SPEAKER_00: Now, if we put those together, plus four in our silica tetrahedron, and we add four oxygens to it, all those oxygens like to be minus two.
• 14:47
  SPEAKER_00: So that's minus eight.
• 14:49
  SPEAKER_00: So we have a minus four charge state thing.
• 14:52
  SPEAKER_01: I don't know if we got lost in the math there or not, but uh yeah, you're uh you're getting a little rambly here.
• 15:00
  SPEAKER_02: Um the uh the listeners they need to forgive you.
• 15:03
  SPEAKER_02: This is uh Dr.
• 15:05
  SPEAKER_02: Professor Jesse Rymanck is a geochemist, okay?
• 15:09
  SPEAKER_02: And so I've getting carried away.
• 15:13
  SPEAKER_02: And uh we're trying to distill this down, Jesse.
• 15:16
  SPEAKER_02: Let's keep things on the simple term, okay?
• 15:19
  SPEAKER_00: The point here is that that image number two, if you just have that thing, it has a minus four charge on it, and that's not stable.
• 15:25
  SPEAKER_00: We need to add some positives to that thing.
• 15:27
  SPEAKER_00: Right.
• 15:27
  SPEAKER_00: And so we need to go around and find other cations.
• 15:30
  SPEAKER_00: Remember, back to our cat is a positive.
• 15:33
  SPEAKER_00: I love saying that.
• 15:34
  SPEAKER_00: It's positive.
• 15:36
  SPEAKER_00: Um, we need more cations to link together with our silica tetrahedron to build a stable neutral mineral in the structure.
• 15:43
  SPEAKER_00: So we need to add magnesium or calcium or aluminum to this to make a mineral.
• 15:47
  SPEAKER_00: So I know I'm getting rambly.
• 15:50
  SPEAKER_00: I'll wrap it up here, Chris, by saying that the silica tetrahedron, we need to add stuff to it so we can have a silica tetrahedron that is bonded to a bunch of different stuff, but not bonded to any other silica tetrahedrons in our mineral structure.
• 16:01
  SPEAKER_02: So let's move on then, Jess.
• 16:02
  SPEAKER_02: The second of the five silicate structures is called the single chain.
• 16:07
  SPEAKER_02: And if you refer to image three in this that shows how this works, if you take the single tetrahedron that we just talked about and you stack these next to each other, in like if you just think of a metal chain, okay, each one of those oval links that connect to each other, that's what a single chain tetrahedron looks like.
• 16:28
  SPEAKER_02: And what's happening with this is that the oxygens on the point of the pyramid are sharing with a nearby tetrahedron and they just link together to form this long, skinny single chain.
• 16:41
  SPEAKER_00: That's nice, right?
• 16:42
  SPEAKER_00: I mean, that's pretty easy.
• 16:43
  SPEAKER_00: We stack them on top of one another, make a big chain, and then we we smash stuff on the edges to make a neutral atom, just like our single tetrahedron.
• 16:52
  SPEAKER_00: We need to add stuff to make a neutral mineral here.
• 16:56
  SPEAKER_00: So that's a single chain.
• 16:57
  SPEAKER_00: We can do one step more complicated, but it's still pretty simple.
• 17:01
  SPEAKER_00: Is uh image number four there is just a double chain.
• 17:03
  SPEAKER_00: So now this means we take two chains, we sort of line them up next to each other, dangle them next to each other.
• 17:10
  SPEAKER_00: I always kind of think of you know those bead curtains, Chris, that some people had in their doors.
• 17:14
  SPEAKER_00: They're dangling together, except you bond those chains together a little right next to each other.
• 17:18
  SPEAKER_00: You just have two of those little bead chains.
• 17:20
  SPEAKER_00: The beads are bonded to each other.
• 17:23
  SPEAKER_00: Again, silica atoms, silicon atoms are sharing oxygens in that way, and you have a double chain.
• 17:28
  SPEAKER_00: What's the next most complicated one, Chris?
• 17:31
  SPEAKER_02: I actually I don't know if this is more complicated.
• 17:34
  SPEAKER_02: I don't I don't think it is.
• 17:35
  SPEAKER_02: It goes back to that's a perfect analogy, by the way, the the beads hanging from a doorway, right?
• 17:40
  SPEAKER_02: A single chain is one strand of beads hanging in a doorway.
• 17:43
  SPEAKER_02: A double chain is two strands of beads hanging in a doorway, and they're connected to each other um across.
• 17:50
  SPEAKER_02: Now, imagine the whole doorway has strands of beads, and they're sharing oxygens between the strands, and so this forms a sheet silicate.
• 18:00
  SPEAKER_00: So that's a sheet silicate.
• 18:01
  SPEAKER_00: And sheet silicates, I like sheet silicates.
• 18:03
  SPEAKER_00: They're maybe my favorite minerals, Chris.
• 18:05
  SPEAKER_00: These are the micas, like muscovite or biotite, these flaky minerals.
• 18:09
  SPEAKER_00: They're used to be used in old window panes because they come off, they peel off in single sheets.
• 18:15
  SPEAKER_00: So you get these really nice just sheets of a mineral.
• 18:18
  SPEAKER_00: And we collected a bunch of this back in the day.
• 18:21
  SPEAKER_00: We we went all over looking for really good books of muscovite or biotite, right, Chris?
• 18:28
  SPEAKER_02: Enormous books, these what we're called pegmatitic, like huge crystals that are all stacked together, like uh imagine a thousand-page book, and each page is a mica or a muscovite or a biotite, and they're all kind of bonded together.
• 18:43
  SPEAKER_02: Yeah, I love the mineral.
• 18:45
  SPEAKER_02: They come in all different kinds of colors, you know.
• 18:46
  SPEAKER_02: You got muscovite, which is clear, and biotite's black, and then everything in between.
• 18:50
  SPEAKER_00: You remember uh our trip where we went to the Black Hills of South Dakota, and I can't remember which mine we're at, the white elephant mine or one of these, but we found some amazing books.
• 18:59
  SPEAKER_00: I mean, we call them books because it looks like a whole stack of sheets on top of one another, but it's actually these minerals that are layered.
• 19:06
  SPEAKER_00: I have one, I've I've kind of converted my wife into a lover of beautiful minerals, and I have one sitting on our bookshelf, and it's in the prime location because it's this beautiful book of flaky, colorful muscovite.
• 19:16
  SPEAKER_00: It's so cool.
• 19:17
  SPEAKER_00: That's right.
• 19:17
  SPEAKER_00: That was that was a great trip.
• 19:19
  SPEAKER_00: I that was one of our best trips for sure.
• 19:21
  SPEAKER_00: Yeah, we had we had some good times for sure.
• 19:23
  SPEAKER_00: All right, so to get more complicated, or one more complicated structural thing is our fifth one, which is our sixth image in the stack.
• 19:31
  SPEAKER_00: And this is what's called a framework silicate.
• 19:33
  SPEAKER_00: And this is where you take those sheets now.
• 19:34
  SPEAKER_00: We have those sheets of the beads curtains all bonded together.
• 19:38
  SPEAKER_00: We have oxygen sticking out of that, though, that can be used to bond between other silica tetrahedron.
• 19:44
  SPEAKER_00: And so, what this is is you just layer sheets on top of one another, basically, except you bond them together between the silica, oxygen, silica again.
• 19:53
  SPEAKER_00: And this makes a what's called a framework silicate.
• 19:56
  SPEAKER_02: Well, yeah, a framework silicate is where every single oxygen in the pyramid, every point of the pyramid is going to be shared with a nearby pyramid.
• 20:06
  SPEAKER_02: And so if you take SiO4 and share every one of those oxygens with another SiO4, the oxygen atoms they belong to two tetrahedrons, they belong to two pyramids, and so that brings the ratio down to SiO2, which happens to be what the mineral quartz is made of, the second most common mineral in the crust of the earth.
• 20:32
  SPEAKER_00: That is a neutral thing.
• 20:34
  SPEAKER_00: There's not a lot of space to fit other cations in there.
• 20:37
  SPEAKER_00: There's not a really a need to fit other cations in there.
• 20:39
  SPEAKER_00: So these minerals are very high in silica and oxygen.
• 20:43
  SPEAKER_00: The ratio of silica and oxygen to other stuff is very low in framework silicates because the silica tetrahedrons are pretty happy.
• 20:50
  SPEAKER_00: They're all bonded together.
• 20:51
  SPEAKER_00: It's pretty happy right there, living that way.
• 20:54
  SPEAKER_02: Exactly.
• 20:55
  SPEAKER_02: So there we have it.
• 20:56
  SPEAKER_02: Those are the five silicate structures.
• 20:59
  SPEAKER_02: Well, Jesse, that kind of brings this episode, episode number two, to an end.
• 21:03
  SPEAKER_02: We talked about the chemical composition of the different layers of the earth, and then we used that, we ended with the chemical composition of the crust of the earth to kind of launch us into the most important and the most abundant mineral group that exists on the planet, which are the silicates.
• 21:20
  SPEAKER_02: And we talked about the five different silicate structures that you can get.
• 21:25
  SPEAKER_00: So you ready for a couple questions here, Chris?
• 21:29
  SPEAKER_00: I think so.
• 21:30
  SPEAKER_00: Go.
• 21:30
  SPEAKER_00: Let's do it.
• 21:31
  SPEAKER_00: Are you going to be criticizing my questions again?
• 21:33
  SPEAKER_00: Or are you going to be quiet?
• 21:35
  SPEAKER_00: Depends.
• 21:35
  SPEAKER_00: Okay.
• 21:35
  SPEAKER_00: Depends on if they're any good.
• 21:37
  SPEAKER_00: I think these are these are relatively straightforward review questions.
• 21:40
  SPEAKER_00: Why is the silica tetrahedron the main building block of rocks on Earth?
• 21:44
  SPEAKER_00: A, silica and nitrogen bond well together.
• 21:47
  SPEAKER_00: B, silica and oxygen are the main elements in the upper parts of the planet, and the tetrahedron is the best way for them to bond.
• 21:54
  SPEAKER_00: C, oxygen is a cation that shares electrons easily with silicon.
• 22:00
  SPEAKER_02: B.
• 22:01
  SPEAKER_02: And by the way, Jesse, you have to be aware of something too.
• 22:04
  SPEAKER_02: When you write questions, the most common correct answer is the longest answer.
• 22:09
  SPEAKER_00: You put more detail into B than you did in the end.
• 22:11
  SPEAKER_00: I know that, Chris.
• 22:12
  SPEAKER_00: I have given enough tests in my day to know that.
• 22:15
  SPEAKER_00: But also, I'm trying to make it a little bit easier for you.
• 22:17
  SPEAKER_00: You struggled last time, so I was trying to make it easier this time.
• 22:19
  SPEAKER_00: Okay, you're right.
• 22:20
  SPEAKER_00: B.
• 22:20
  SPEAKER_00: All right.
• 22:21
  SPEAKER_00: Silica and oxy are the main elements in the upper parts of the planet, and that's just the tetrahedron, just the most efficient way for them to go together.
• 22:28
  SPEAKER_00: Okay.
• 22:28
  SPEAKER_00: All right, question number two.
• 22:30
  SPEAKER_00: What is the most connected arrangement for the silica tetrahedrons?
• 22:34
  SPEAKER_00: Is it A framework?
• 22:36
  SPEAKER_00: B double chain or C sheet?
• 22:39
  SPEAKER_00: Framework.
• 22:40
  SPEAKER_00: Framework.
• 22:41
  SPEAKER_00: Perfect.
• 22:42
  SPEAKER_00: Framework, then sheet, then double chain, then single chain, then floating single tetrahedron, right?
• 22:48
  SPEAKER_00: In order of most complicated or most connected to least connected.
• 22:51
  SPEAKER_02: Yeah.
• 22:52
  SPEAKER_02: All right, that's a wrap for this episode.
• 22:54
  SPEAKER_02: And in our next episode, we're going to talk about the other mineral groups and then something called the rock forming minerals.
• 23:00
  SPEAKER_02: Perfect.
• 23:01
  SPEAKER_02: See you next time.
• 23:02
  SPEAKER_00: Take care.