This video has been sponsored by Nord VPN. Right now they're offering 75% off 3 year plans, as
well as one month free, which you can get by going to nordvpn.com/nilered. As a kid I can sometimes
remember looking through dirt, and finding little bits that looked almost like gold. And almost
every time, I would get really excited thinking that I was rich or something, only to be quickly
shut down, and told that it was worthless fool's gold. At the time I kind of just accepted that
answer, and I threw away what I had found, without really questioning much. What I didn't know though
was that despite it being way less valuable than gold, it was still a really interesting compound.
The mineral name for fool's gold is pyrite or iron pyrite, and its chemical name is iron disulfide.
It's chemical formula is pretty simple just FeS2, but what makes it really cool, is the different
ways that it can crystallize. The appearance that it ultimately takes on, will depend heavily on the
environment that it was formed in. Some important factors that affected, are things like purity,
time, pressure and temperature. For example pirate from a certain region in Spain, tends
to form these oddly perfect looking cubes, which honestly still kind of look fake to me. Their size
and distribution can also vary quite a bit, and some crystals can get really big like this one.
The base unit cell that builds the pyrite crystal is cubic, and under these circumstances,
the macroscopic crystal that formed, was cubic as well. However, impurities and the other conditions
that I mentioned earlier, can alter how these units build on each other, and it can affect the
final appearance. So depending on where you are in the world and what the geological conditions are
in that place, it can look quite different. For this video, I'm gonna be focusing on pyrite, but
I did want to mention that it is possible, for the iron disulfide to have a non cubic unit cell. It
can instead be something called orthorhombic, and when this happens, it forms a different mineral
called marcasite. This one's a lot more brittle though, less stable, and has a different color. In
any case, now that we know a bit about what fool's gold is in general, I want to dive a bit more into
its physical and chemical properties. So to start off just in appearance and feel, I think it's
really similar to metal, and color wise, it can be close to that of gold, and it's also often found
in the same area as gold, so it's not surprising that they can sometimes get mixed up. The biggest
difference though, is that gold is never found as these sharp and highly ordered structures,
and it's usually just found as an amorphous chunk like this. And another major difference is that
gold is really soft and malleable, whereas pyrite is really hard and brittle. So if it's hit with
something like a hammer, the pirate would shatter into pieces, whereas the gold, would just get
flattened. Also in terms of its density it's only around 5 grams per cubic centimeter, whereas gold
is about 19.3. With small quantities it might be hard to tell, but once you get a decent amount of
the pyrite, the weight difference is pretty obvious. So when a big chunk is found it's
relatively easy to tell a difference, and it's only really an issue when you have lots of small
bits. For example here, in a clip that I found on YouTube, it really does look like gold. However
this was only because the really shiny pyrite was reflecting a lot of the light from the sun,
and making it hard to tell its color. Once he moved to the shade though the brassy yellow color
of the pyrite became quite evident, but the color of the gold stayed the same. His other simple test
was based on the fact like I mentioned before, that the density of pyrite is way less than that
of gold. Just by gently swishing around the water, the heavier gold is able to stay put,
but the lighter pyrite is moved around. From its overall metallic and shiny look, a lot of people
would think that it's conductive and, well they're right it kind of is. It's not nearly as conductive
as a proper metal though, and it's classified as a semiconductor. In general, semiconductor
materials are used pretty extensively in the electronics industry, and it has been suggested,
that pyrite might have some use there as well. Currently I think the major use of it related to
things that are electronic, is in non-rechargeable energizer lithium batteries. In this battery,
one of the electrodes is the lithium itself and the other one, is made by coating iron disulfide
on a thin layer of aluminum. Okay so now for the fun part, where I get to play around with it,
and learn more about its chemical properties. It would have been insane to sacrifice my really nice
cube so instead, I bought a bunch of ugly ones from eBay. I really don't remember exactly how
much it cost, but it was quite cheap, and probably only around $20 for the whole bag of them. For
the first test, I just put a small amount of concentrated hydrochloric acid, on one of the
pieces. I let it sit there for a few minutes, but it didn't look like much was happening.
There should have been a reaction going on, but I just think it's really slow. The iron disulfide is
FeS2, but I thought that it might react faster if I converted it to just FES. This can be done
pretty easily by just heating the pyrite to its decomposition temperature, which starts at around
540°C. To do this, I just carefully shot it with a blowtorch until it looked like the surface was
turning black. Some pieces of pyrite also started cracking off, but I'll talk about that in a bit.
When it cooled down, I added the HCL again and the effect was very subtle,
but it was there. Like last time, I left it for a few minutes and when I removed it,
almost all of the blackness had disappeared. The HCL had also taken on a yellow color,
which you can see on the paper towel. So the major thing that happened here was a reaction between
the black FeS that I made, and the hydrochloric acid. This lead to the formation of Fe(ii)Cl,
as well as hydrogen sulfide gas. The amount that was reacting here was so little though that it
wasn't really possible to see any gas coming off. However I wanted the effect to be much clearer so
I decided to try heating the pyrite more, and to convert as much as I could to the FES. Initially
it looked decent and the whole surface was turning black but then suddenly, pieces of it started to
shoot off. I'm not 100% sure what caused this, but I think it is a direct result of the decomposition
of the FeS. In order for it to break down to FES, it needs to kick off a sulfur. It's fine if this
happens on the surface of it because the sulfur just boils off, and then burns in the air to make
SO2. However if this happens in the cube, there's no place for the sulfur gas to go. So I imagine
that it starts building up pressure, and it eventually gets to a breaking point. To a certain
extent there's also probably some water mixed into the mineral, which also can cause it to explode. I
continued heating the large piece that remained and initially some pieces did come off of it,
but eventually it stopped. I'm not exactly sure why it stopped breaking apart, but I'm assuming
that it was somehow able to release some of the gas pressure. I kept heating it until most of
it had become red-hot, and then I let it cool down. As it cooled, the surface of it slowly
got oxidized by oxygen in the air to make what I assumed was red Fe(iii)2O3. When it eventually got
to room temperature, I thought that it was pretty interesting, because it didn't look like the
fool's gold at all anymore. There was absolutely no goldish yellow color left, and it was all just
black and red. Like I just said, I think the red stuff was Fe(iii)2O3, but I'm not sure
if the black stuff was FES, or Fe(ii)O. I tried testing it again, by just adding some hydrochloric
acid to the surface of it, and it kind of just soaked it up. If you recall from before though,
when I tried this with the intact pyrite, the acid just sat there. So apparently as it decomposed,
it got a lot more porous. I broke it apart with a hammer, and what I thought was cool,
was that it was possible to see all the different layers. On the outside was the fully reacted and
oxidized stuff, but then right underneath it was a layer of black FeS. Then just below that was
the still fully intact FeS2. I really thought that the heat penetrated much deeper, but apparently it
didn't. Onto this I tried adding the hydrochloric acid again, and it worked a bit better. It was
possible to see a small amount of bubbling, but it still wasn't as good as I would have liked it
to be. To get it to react vigorously, I would need to convert a lot more to the FES. And to do this,
I first had to crush it up. This really isn't very hard to do though, because the pyrite is
actually quite brittle. So I just added some of it to a mortar, and started bashing it. This was
what I had after a few minutes, and I probably could have crushed it a bit more, but I figured
this was good enough. This was all added to a test tube, and I did my best to flush it with nitrogen.
Then just like all the other times I blasted it with a blowtorch. The reason I used the nitrogen,
was that I hoped without any oxygen present, the sulfur would be able to come off, and knock it
immediately converted to SO2. After only heating it a bit, it all started turning black, and I
could see that there was a gas being released from the powder. Because of the background it
was hard to see, but there was also a white vapor that had filled the tube. At the time,
it didn't occur for me to test it, but it was almost definitely sulfur maybe along with a
bit of water vapor. What I think is cool, is that industrially, pyrite is used in a very similar way
to this, to generate elemental sulfur. Depending on the purpose, the sulfur can be kept as is,
or can also be converted to SO2 for the paper industry, or even to SO3,
to make sulfuric acid. When I felt like most of it had converted to FES, I stopped heating it,
and I let it cool. I probably should have refilled the tube with nitrogen though,
because as it cooled, the surface was oxidized and it turned red. I figured this was fine because
most of it was still black, but then I mix things, and saw there was still a whole bunch of pyrite.
I apparently had the same issue as before, where it only really converted the stuff on the outside,
and the stuff in the center, was more or less intact. This time though, I thought I still
made more than enough, so I continued on with the testing. When it got to room temperature,
I dumped it all onto a dish, and it honestly kind of looked the same. Nonetheless I took a
small sample of it, and I placed it onto another dish, and tried adding hydrochloric acid again.
This time the reaction was way more vigorous, and a gas was definitely being produced. H2S
is extremely potent, and even in small quantities it smells like rotten eggs. So a very simple test
for it, is technically just to try and smell it. This was all done in my fume hood though,
which apparently worked quite well, because I didn't smell anything. The only real way for me to
smell it would be to bend over and to get really close to it. The problem with this though, is that
H2S is also super toxic around the same level as cyanide gas, so I wasn't too excited about
trying to take a breath of it. The much smarter thing is to instead use test strips. These are
made pretty easily by soaking paper in a solution of lead acetate, and then letting it dry. Now if
I was in fact making H2S, then the lead acetate on these strips, should be able to react with it,
to make black PbS. And when I did this, that was exactly what happened. I was making the H2S here
mostly as a demo, but in general it is a useful chemical. In the lab, it's usually produced the
same way, where a strong acid is reacted with FeS. However the FeS is rarely made from pyrite, and
it's usually either purchased, or made directly, by reacting iron and sulfur powder. It leads to an
extremely exothermic reaction, and this is a clip from one of the first videos that I ever posted
to this channel. The videos that I made back then were totally different, but if you're interested
in checking it out, there's a link in the description. In any case I think that's about it,
pyrite might not be as nearly as valuable as actual gold, but I think it has enough of its
own unique properties and uses, that it more than makes up for this. And honestly, I think the cheap
price is actually a good thing, because it means that most people can buy it relatively easily.
For example, I think the large cube sample that I have, is one of the coolest things that I own,
but it only cost me something around $100. In Canadian dollars, that's about two grams of gold,
which is not only not very much, but also nothing really impressive to look at. In any case,
this was the first video that I did on a mineral and I had a lot of fun doing it. I definitely plan
to do this again with another mineral, so in the comments, let me know what you'd like to see. I
ended up getting really behind schedule editing this video, so I'm probably gonna be posting it
from the airport, on my way to Japan for vacation. To do this though, I'll have to connect to the
public airport Wi-Fi, which isn't really secure, and kind of makes me nervous. However luckily,
services like Nord VPN exist, which allow me to keep my data safe, by encrypting everything that's
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said, I've been using Nord VPN for about a year now, and I highly recommend it. Also right now,
they're offering a great deal, that gives you 75% off their three-year plan, as well as one
extra free month. You can get this by going to nordvpn.com/nilered, or by clicking the link in
the description. As a side note, some of you might be wondering why I'm posting the video on the way
to Japan, and not when I get there. My answer to this is kind of simple, where A I don't really
want to be working on videos once I get there, and B I just think it could be fun. I'm gonna be
having a 14 hour plane ride between Minnesota and Tokyo, and I just thought that it could
be interesting, to buy Wi-Fi and to answer your comments from the air. As usual a big thanks goes
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