Bismuth - a surprisingly rare metal

Bismuth - a surprisingly rare metal

Bismuth (Bi) is a metal (though sometimes classified as a metalloid) best known for the beautiful crystals if forms when cooled from a liquid state. Other uses for metallic bismuth are rather limited, usualy replacing lead in applications where a toxic metal is not an optimal choice, such as soldering, fishing or hunting.

Being only around as abundant in the Earth's crust as silver (Ag), such metal is not a resource to be implemented widely in such mundane tasks anytime soon.

Bismuth metal pieces.

Pure metallic bismuth is a silvery, shiny metal that oxidizes on air when heated. Otherwise Bi is classified as highly unreactive metal, just below copper and mercury. It is also surprisingly brittle and can be broken up by hand. That makes it useless in structural roles, at least in the pure, unalloyed form. Reagent grade bismuth can be bought in the form of small, needle-like drops or bigger bars that can be broken into smaller pieces.

Vanadium - the secret hero of metallurgy

 Vanadium - the secret hero of metallurgy

Vanadium (V) is the lesser known among the lighter transition metals, located between the popular titanium (Ti) and chromium (Cr) it kind of gets overshadowed. The importance of vanadium, however can not be overstated. It plays a huge role in improving hardenability, tensile strength, tribological wear resistance and hardness of steels.

Pure V crystals.

An ampoule of V crystals.

Neodymium - the most popular of rare earth metals

Neodymium - the most popular of rare earth metals

Neodymium metal is generally very well known, compared to it's cousins from lanthanides row - ask a random person about neodymium and they will probably at least recognize the name from somewhere, whereas thulium (Tm), gadolinium (Gd) or dysprosium (Dy) would most likely be a different story.

Pieces of neodymium metal under paraffin oil.

The main reason why is not the metal itself, but neodymium magnets, which will be talked about a bit later. Pure neodymium in it's metallic form is a shiny graish-yellowish-silver metal, which oxidizes rather rapidly on air, firstly getting covered with a dull black coating, which as time passes flakes off into what looks like a pink colored dust that serves no purpose in keeping the metal from further oxidation. 

The pink dust is Nd2O3, neodymium oxide that is often utilized in ceramics or glass making.

Neodymium glass bottle.

Nd3+ doped cubic zirconia stones

When added to glass, neodymium on +3 oxidation state dyes it purple-violet color that turns sky blue under fluorescent light. Similiar coloring can be observed on synthetic zirconia stones. Those look lighter and clearer than the traditionally dyed purple zirconias doped with manganese (Mn) ions.

Small cylindrical neodymium magnets in a jar.

Neodymium, sometimes called also rare earth magnets (that groups contains also Sm-Co magnets), are an alloy of iron, neodymium and boron. Due to their brittleness, these magnets are usually coated with a thick layer of nickel (Ni). An addition of dysprosium (Dy) can also be used to improve such magnet's resistance to demagnetisation. 

Nd2Fe14B magnets are currently the strongest permanent magnets available and can be purchased in many different sizes. Small 2x2 cylindrical magnets, like the ones pictured, are popular among 3D printing enthusiasts for adding magnetic locks or creating satisfying fidget toys etc..

Tellurium - a surprisingly rare element

Tellurium - a surprisingly rare element

Tellurium is one of the rare instances, where finding a pure sample is much more likely than any of the compounds. It belongs to the least abundant stable elements in the Earth's crust, with rarity comparable to these of platinum group metals or gold. It is however not a metal, but a metalloid with properties similiar to these of selenium (Se) or sulfur (S) of the same group - chalcogens.

Pure tellurium in a jar.

Tellurium in it's pure form is silvery white, but over time, especially when finely divided, it might develop a thin layer of surface oxidation that causes it to take different colors, as observed on some of the more reactive transition metals. It's also surprisingly dense - with the density of 6,24 g/cm3, for a given volume it's heavier than titanium, vanadium, gallium and many other metals.

Pure tellurium chunk.

As typically observed in metalloids, Te is also extremely brittle. So brittle in fact, that just picking it up with a pair of tweezers and placing it to take a photo, caused all the crumbles visible above to separate from the chunk. For that reason, any glass bottle or ampoule that tellurium is kept in will quickly get coated with a layer of microscopic dust and lose it's clarity. 

Brittleness of tellurium gets even more annoying when you learn how toxic and problematic it is when it enters a human's body - even in relatively small amounts, tellurium compounds are able to make a person smell terribly for a long time. It is also able to be absorbed through the skin, so it's best to avoid handling it bare handed at all.

Coming back to what was mentioned in the first paragraph, compounds of tellurium exist in nature primarily in the form of metal tellurides, with the most well known being gold telluride calaverite and gold-silver telluride sylvanite. These minerals are rather expensive from a collector's perspective, especially compared to pure, plain metalloid form.

As a fun fact, metal tellurides, like CdTe, are used in production of photovoltaic cells and infrared radiation detectors. Most of the naturally existing Te is also composed of technically radioactive isotopes, however their half-life is long enough to be considered stable.

Americium & Neptunium - seemingly unobtainable elements

Americium & Neptunium - seemingly unobtainable elements

Both Am and Np metals have high atomic numbers, 95 and 93 respectively. That means both of them are above what is considered to normally occur in Earth's crust (at least in any larger quantities, as trace amounts of neptunium can be found as a product of spontaneous fission of U-238 or neutron induced fission of U-235 etc.. Am isotopes also can't be completely excluded, following this line of reasoning). Both of these elements are also pretty radioactive. Neptunium is more stable, with the longest-living isotope Np-237 having half life over 2 million years, which is still about 2000 times shorter than the natural U-238's.

Americium, on the other hand, is an absolute menace when it comes to the stability of it's isotopes.

Steel casing of a radioactive smoke detector.

That doesn't mean scientists weren't able to tame such powerhouse of a nucleus - they did, and some of us might be able to find the proof a couple of meters from their heads. Am-241, an isotope with a half-life equal to around a quarter of the terrifying isotope Ra-226's 1600 years, is used as a source of alpha particles that help detect when anything goes wrong during cooking.

Americium smoke detectors utilize the small button inside as a source of near continuous radioactive decay that causes air around it to ionize. An electronic circuit inside is able to tell when something (like smoke) goes in the way of the electron flow through the ionized air (lowers the passing current) and force an alarm to go off.

Americium-241 button source

So by getting a simple, cheap smoke detector, you might be able to get a sample of an extremely radioactive element, in the form of a small piece of metal foil containing AmO2. Might be a little underwhelming, but trust me, you wouldn't want much more. Also, if you ever get your hands on such an item, please don't tamper with it in any way. 

Keep it sealed, don't poke at it, scratch it, eat it or play with it anywhere you might want to live afterwards. And do not remove the steel piece that contains said foil! Radioactive contamination is not a joke and even a small source should be treated responsibly.

And why did I mention neptunium? Most isotopes of americium, including what is inside the smoke detectors, decay to neptunium. Meaning that after some years, your Am-241 button can contain a fair bit of Np atoms. It's the only way th get the element if you aren't satisfied with keeping pitchblende as a sample of all the lower actinides.

A piece of U ore might contain an atom or two of neptunium.

Don't play with radioactive stuff and don't go searching for metallic forms of these elements. You will get put on a list and won't be able to find them anyways.

Nickel - the corrosion resistant one

 Nickel - the corrosion resistant one

Nickel is one of the metals that aren't hard to find in everyday life, but are infinitely more common in the form of thin coatings or alloys. Addition of nickel in steels helps stabilize austenitic microstructure in room temperature, which, together with chromium, can make steels resistant to corrosion in some of the most problematic acids, like nitric or dilute sulfuric acid.

Pieces of nickel anode.

Relatively pure nickel sheet can be bought as sacrificial anodes for electroplating. I got such anode in the form of a small strip, which I divided into smaller pieces that could fit my sample jar. In such form, the interesting yellowish tinge of nickel metal is easily visible.

Nickel spheres.

Pure nickel metal can be also bought in the form of small spheres produced through decomposition of nickel tetracarbonyl gas on heated nickel seeds (Mond process). Such spheres make for a really nice sample and can range anywhere from under a gram to impressive, cluster-like rounds weighing in hundreds of grams.

Brass coins plated chemically with Ni.

As mentioned before, nickel is used to plate everything, ranging from steel parts (such as barbells, shackles or jewellery), through neodymium magnets, to even polymer items, like car bumpers. It is most often utilized paired with a thicker copper coating beneath to improve the adhesion - that's why many nickel plated items, when subjected to everyday wear, tend to go more into the copper's color range.

Such plating can improve the corrosion resistance, structural integrity (in the case of brittle ceramics), and overall looks of the item.

Nickel coatings can be made through electrochemical and chemical (electroless) processes, with the main differences being the use of direct current and the composition of plating baths. Electroplating also utilizes sacrificial anodes, such as the one I cut into pieces (or bigger Mond rounds).

The quality of plating on the steel plate seen below can teach one crucial lesson regarding any form of surface engineering - correct preparation of the plated surface is the only way to achieve a well adherent, aesthetic plating.

Crudely electrochemically plated steel.

Ni coating on NdFeB magnets.

316L austenitic steel.

Lithium metal from a supermarket

 Lithium metal from a supermarket

Lithium (Li) is a metal that is rather sought after by collectors - at least in it's pure, unoxidized form, as just a couple seconds of contact with atmospheric air is enough to turn it into an oxidized mess. Lithium is also incredibly difficult to keep clean even in seemingly inert environments as it's prone to reacting with nitrogen gas most other metals are completely unreactive to in normal conditions.

10x40mm borosilicate ampoule with 0,2g of Li.

When covered by mineral/paraffin oil, Li is fairly resistant to atmospheric oxidation due to low permeablity of air through a layer of oil. Unfortunately, lithium has another trick up it's sleeve - it's also incredibly light, being around two times less dense than water and said oil or over 42 times less dense than the densest stable element - Osmium (Os).

This property causes lithium metal to float on the surface of anything that might try to cover it, exposing itself to air. These are precisely the properties that made me buy a premade ampoule in addition to my self-made sample.

My trick to keep the oil covered metal in a relatively acceptable condition was to insert a piece of sponge into the neck of my jar and to fill everything with oil to the top - this way there was a physical barrier that prevented lithium from floating, while, being saturated with the medium, it also protected it.

Lithium metal pieces under paraffin oil.

That being said, pure lithium metal in pieces or wire is not easy to source locally, so sacrifices often have to be done and other form of the metal used. In the form of foil it can be found in batteries - AA type batteries (the lithium ones, of course) contain a whole roll of the foil, while small button cells have only a bit of it at the bottom. In my opinion however, you will be better off just saving them as separate samples, because cutting them up to free the piece of foil is not only rather unsafe, but also will result in something far from a good looking sample.

Lithium 3V button cells.

A chunk of lepidolite.

An additional sample I got because of the interesting looks was a piece of lepidolite mineral. It's an ore of potassium and lithium with an impressive formula K(Li,Al)3(Al,Si)4O10(F,OH)2. Lepidolite is a mica mineral, meaning that it consists of multiple thin flakes that sparkle nicely but, unfortunately, it also crumbles easily. As a bonus, lepidolite is also an important source of the incredibly rare metal rubidium (Rb), which tends to substitute potassium in it's structure.

Cobalt is pretty easy to come across!

Cobalt is pretty easy to come across!

Despite pure cobalt metal (Co), as show in the form of electrolytic flakes below not being all that easy to get outside specialized sources, cobalt ions and alloys are rather widely available.

Flakes and pieces of pure electrolytic Co metal.

First of all, cobalt metal is an alloying element in many steel types, such as high speed steels (HSS-Co in this case). Addition of cobalt works well in increasing the overall hardness and wear resistance of steels, but also helps keep these characteristics in high temperatures the tools are working in.

Cobalt, however hinders the ability to create martensitic microstructure in steels through increasing the critical speed of cooling required to fully transform the microstructure. Therefore this metal is mostly added in small amounts and in applications that require the benefits.

HSS-Co drilling-tapping bit with TiN coating.

Another way to come across cobalt, this time in the form of Co2+ and Co3+ ions, is to go to an antique store or just look through glass items in your house. My samples of cobalt glass are in the form of a tiny glass bottle and a marble from a well over 100 year old set. The deep blue color is usually achieved through addition of cobalt oxides or other compounds, like carbonates to molten glass. Depending on the saturation of the additives, such glass can look almost opaque and black, but looking through it at a light source will usually reveal the wonderful color.

Cobalt glass bottle.

Cobalt glass marble.

Cobalt doped zirconia.

I've also learnt that cobalt 3+ ions are used to give synthetic gemstones, particularly cubic zirconias (c-ZrO2) a light violet/lilac color. That's why I also included a photo of such stone from my collection.

Thermite cobalt metal (or Co-Fe alloy).

Before owning any pure samples of cobalt metal, I had been trying to produce it myself through an aluminothermic reduction of cobalt oxide with fine aluminum powder. I used a sparkler to initiate the reaction, as it needed a fair bit of encouragement to start, and as a result, I received some small beads of cobalt and a light blue coating on every surrounding surface. The metal is without a doubt heavily contaminated though, as the steel rod inside the sparkler has partially melted from the heat of the reaction.

Low pressure ampoules of Hydrogen, Nitrogen, Oxygen and five of the noble gases

 Low pressure ampoules of Hydrogen, Nitrogen, Oxygen and five of the noble gases

10x40mm ampoule, borosilicate glass.

I managed to get these ampoules from an American site some time ago. Because of lowered pressure inside of them, compared to atmospheric, the gases should be able to glow when subjected to passage of free electrons inside.

I haven't been able to test that yet, probably due to my cheap tesla coil being barely able to excite a neon indicator bulb. I can't however exclude the possibility of these ampoules being produced incorectly (e.g. with too high of a pressure inside), as from what I heard, that had been the case with some purchased by other people.

Most of these gases should be able to glow in different colors in the colder gray - sky blue - violet spectrum, with the main outstander being already mentioned neon that glows with a beautiful warm orange color. Helium has also been observed to glow with similiar color, but the whole thing seems subjective.

One of the noble gases that hasn't been made into such ampoules is radon (Rn). Isotopes of radon however, are among the daughter isotopes of natural uranium and thorium, so a symbolic sample can be prepared through sealing a source containing these elements. Unfortunately, it won't glow at all.