I Made a Glowing Rock From Scratch

[00:00:00]This glowing rock from the shores of Lake Superior is called cyanite, but you probably know it by another name, but that name is actually trademarked. So, yeah. Anyways, these glowing bits are a mineral called sodalite. Pretty cool.

[00:00:13]But there's a closely related mineral called hecmanite that does something even cooler. It changes its actual color in response to UV light. It's pretty neat. And so, I want to try and make it completely from scratch. A few weeks ago, I was reading up on how aluminum ore is refined into pure metal. And I noticed a step called desilication where silica impurities are removed from the ore by digesting it in a hot sodium hydroxide solution forming sodium silicate and sodium aluminate which can go on and react with one another to form insoluble aluminosilicates. So by sacrificing a bit of aluminum here we can create a clean solution of sodium illuminate that goes on to be pure aluminum leaving behind a solid waste product. Basically a pile of microscopic rocks and that's pretty cool. I grow crystals as a hobby, but these are almost always water- soluble crystals.

[00:01:01]And so I figured I could use this same aluminum reaction to actually grow real insoluble minerals for a change. The first mineral that came to mind was sodaly, a really well-known aluminosilicate mineral. It has a very specific atomic structure built from silicon oxygen and aluminum oxygen tetrahedra. These tetrahedra link at the corners to form a cage-like structure called a beta cage, which is the perfect trap for interesting ions. that can cause neat luminescent effects just like in the hackmanite and the this cage is the building block of sodaly and its relatives. How these cages link together is what separates them. Sodaly is much more compact and periodic serving as a much more reliable trap for dopants.

[00:01:42]Now, if we looked at that waste product from the desilication process, that pile of rocks, I wouldn't be surprised if you found some particles that already are pretty similar to sodaly, but they would be among a chaotic mix of different aluminosilicates, not just pure sodalite. So, to make these really cool variations of sodalite, like hackmanite in that one popular rock where the exact crystal structure controls the optical behavior, I needed more control over the reaction. So, let's take a look at what we're trying to build at a molecular level. Remember, the basic building block here is that beta cage, which carries a netg -3 charge. To move closer to neutrality, positive sodium ions find their way inside to stabilize it.

[00:02:22]Although, the most stable configuration of these sodium ions is not three, but a total of four ions on each of these hexagonal faces. So, now the cage has a beautiful positive one charge. And how the mineral deals with this final charge dictates everything. And it all comes down to sulfur. Regular pure sodalite uses a chloride ion to balance the charge. This creates a highly stable electron configuration that requires extreme ionizing radiation to do anything interesting. And well, we have that, but maybe for another video. For now, this type of sodalite is clear and it's boring. In some of these cages, though, if the charge is balanced with a triculfer radical annion, things get a little more interesting. This radical stabilizes the cage but retains an unstable electron configuration. Its electrons can be easily excited by 600 nm light absorbing the warmer colors of the spectrum and making the crystal appear blue. This is what we see in minerals like lazerite, the main ingredient in good old lapis lazuli.

[00:03:23]That's cool, but it gets cooler. If we have a dulfide radical balancing that charge instead, the electrons are configured to absorb ultraviolet light at around 365 nanome. This promptly promotes an electron to an unstable higher energy level which immediately decays back down to the ground state.

[00:03:40]During this decay event, the absorbed energy is re-released partially as lattice vibrations and partially as lower energy orange light. This leads to a secondary glow that we call fluoresence that we see in this famous particular sodalite bearing rock.

[00:03:55]Finally, the coolest effect teneerence.

[00:03:58]If we do something crazy and consider two cages both positively charged and instead of satisfying both cages individually we slap a dvalent dulfide ion with a -2 charge into just one of the cages leaving the second cage with a vacancy and a localized positive potential. If you watched our video on putting salt through the particle accelerator you may be able to recognize what happens next. If we look at the potential field of this two cage system, we see that there is a deep potential well located right at the unoccupied beta cage. A perfect trap for electrons.

[00:04:34]But how do we get the electrons into this trap? Well, conveniently UV light is high enough energy to ionize the dvalent dulfide ion kicking an electron out to explore the lattice until it falls into the empty cage and gets stuck in that potential well. This trapped electron is called an F-enter and it behaves like a particle trapped in a quantum box absorbing visible light centered around green and yellow making the mineral appear purple. For a much more in-depth explanation of Fenters, I highly recommend you check out our salt video after this one. So, as long as this electron is trapped, the mineral appears purple. But the electron does not remain trapped forever. Regular old visible light has a chance to excite the electron and push it out of the well, allowing it to recombine with the dulfide and for the purple color to disappear. Okay, so this is cool and all, but how do I make it? Well, we know that these beta cages can be formed through a series of reactions involving sodiumsicate and sodium aluminate. So, I dissolved some silicon metal in some aluminum foil into sodium hydroxide. I then mixed this sodium aluminate and sodium silicate which immediately formed this thick dense aluminicate hydrogel. I stirred it up and then I added salt to provide the sodium and chloride ions necessary to build the beta cages. But this uh soup of ingredients won't form beta cages just by itself. I need to digest this. So I stuffed it inside this hydrothermal reactor and put it in a furnace at 200C for about a week. The reactor prevents the water from boiling so it can reach temperatures well over 100 C to allow the components to break down and reassemble themselves into four and six membered aluminosilicate rings.

[00:06:16]These rings are our puzzle pieces that make up the beta cage and they're attracted to these islands of bound sodium and chlorine floating around in the solution and symmetrically assemble around it until we have a complete beta cage. So, after letting this go for about a week, I opened up the reactor and I was immediately hit by the most intense smell of rock. This stuff smelled so strongly of just rockiness.

[00:06:40]It was crazy. I dumped out this alkaline goop and then rinsed it and dried it into a fine powder. And here I successfully made some boring sodalite.

[00:06:50]What I need to do now to turn this into hemanite is to squeeze some dvalent dulfides into these cages somehow. I mixed the powder with some sodium sulfide. The sulfur in here is already pretty reduced at a minus2 oxidation state, so we're in the right direction.

[00:07:05]I heated up this mix to about 850C, hoping that the thermal energy would open up these windows in the beta cage and maybe force some sulfur species into the cages. To prevent the sulfur from oxidizing and just doing nothing, I packed the powder into a crucible mixed with some charcoal powder to create a reducing atmosphere during the processing. And so after an hour at 850C, the powder had weakly centered into this chalky mass. Hopefully when I shine this UV light on it, it will turn purple.

[00:07:36]Well, it's it's not purple, but it's not nothing. I actually expected this to not work at all, but it turns out it halfway worked. I didn't get the hackmanite that I was going for, but I did get the fluorescent sodalite that shall not be named, which I mean is is still super cool. So anyways, I can think of two likely things that may have happened here. I failed to form any dvalent dulfide ions and only formed dulfide radicals. Or I did make some dvalent dulfide ions, but I had no adjacent chlorine vacancies to form electron traps. Or maybe I did make dvalent dulfide, but the molecule just can't fit inside of these hexagonal windows even when they're stretched from the heat. Or maybe it was all of these things. So, I spent weeks tweaking the variables. I tried both open-faced ingot processing, closed graphite crucibles buried in charcoal, a wide variety of processing parameters and times, and even a few fluxes as well. But no matter what I did, I just kept getting this orange glow, no tennerence. So, it was time for a larger change. I made some new aluminosilicate gel, but this time I added some aluminum sulfate directly to the gel itself. The goal here was to force sulfate ions directly into the cages during the actual assembly rather than forcing in sulfur afterwards into a pre-built beta cage. I would then reduce the sulfates into sulfides at high temperatures in a reducing atmosphere and perhaps some of these now volatile sulfide ions wander around and interact with other sulfide ions in adjacent cages to form dvalent dulfides and vacancies. The result though, garbage, not even any fluorescents.

[00:09:16]I'm guessing that the concentration of sulfate ions wasn't high enough to incorporate them into the beta cages as they formed. So instead, I added a standard handful of sodium sulfate to the next batch and began more hydrothermal processing to see what would change. And same old story, just orange fluorescent, no tennerence. One interesting thing though was this obvious formation of lazarite along with it. I hadn't seen this yet and it was pretty cool. But still with no tennibresence, the only other avenue I could think of exploring was literally just making polyulfides from pure sulfur and adding that to the gel. And so let's see what happens. Now after processing, we can see that our sodalite does have some interesting colors, but still no tennibresence.

[00:10:02]This blue fluoresence, though, I literally have no idea what that is. And so at this point, I was looking at more systematic issues. And I thought that because my product is a powder, perhaps a very light color change like what is observed in tennibresence would be impossible to see because of the light scattering. So to verify this, I took some real hackmanite and crushed it up into a fine powder. And sure enough, it doesn't look purple anymore. It looks white. So in this case, maybe I did make a tenner material, but the light scattering is just preventing it from being observed in the first place. To test this, I took every type of sodalite that I synthesized and I added some mineral oil, which has a similar refractive index to sodaite. And we can see that immediately after adding it, the colors begin to pop. So hopefully when I shine the UV on it, we'll see the intrinsic color of one of these powders change just like real hackmanite. And well, unfortunately, besides the real Hackmanite powder, I don't see any difference in color between the before and after photos here. And well, I'm now officially out of ideas except one. We could run my powders through the lac.

[00:11:03]Intense electron or irra radiation does have a tendency to induce some crazy atomic defects. So maybe it'll do something. Although I'll save that for another time. Making this fluorescent chalky sodalite is still super cool. But if anyone more experienced in this realm of chemistry has any suggestions on what they would do differently, please let me know because I'm no means an expert and I'd love to try it out. Anyways, sort of like the inner metallic crystal video. I made tons of this stuff. So, if any of our current or new Patreon supporters also find this interesting, just send us a message and we'll ship you out some.