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Acid and Gold: The Modern Alchemy of Artificial Gemstones
Everyone knows that humans can make artificial diamonds. But did you know that we can make sapphires, emeralds, and rubies as well? Did you know that this involves weird occult-like instruments, like little rooms lined in gold? Starting with crystal seeds and watering regularly with hydrochloric acid, we can grow a cluster of emeralds.
Sometimes you get the feeling that ancient alchemists would look at the methods we use to turn liquids into meat, turn powder and liquid into pillars of ash, or turn shapeless globs into car tires, and ask us why we think they employed crazy techniques. The strange, elaborate methods that we use to transform one form of matter to another would leave most people scratching their head and wondering why anyone thought that would work. Of course, they do actually work. Applied chemistry is often just alchemy made effective. But that doesn’t make it any less bizarre. And one of the more bizarre things we do is turn relatively worthless materials into precious gemstones.
Emeralds
To make a synthetic emerald, you need an airtight gold oven. One would think that, if you had a gold oven, you wouldn’t need to get into the emerald-making business — but to be fair, it only needs to be gold-lined.
Gold doesn’t react with much, so it won’t interfere with the process that is going to be happening inside it. In nature, emeralds form near hydrothermal vents, under tremendous heat and pressure. They are beryl with the addition of chromium and vanadium, both of which color the crystals green. When people want to make them, they put chromium and vanadium, as well as silicon, oxygen, aluminum, and beryllium, in the aforementioned gold-lined oven. These materials are clustered around a beryl seed on a platinum wire. They crank up the pressure and the temperature, and pour hydrochloric acid on the whole set-up. The acid keeps the coloring materials from precipitating out of the gems as they grow. Over the next month or so, they grow about a millimeter a day, until they’re ready to be harvested.
Synthetic emeralds are chemically and structurally identical to naturally occurring emeralds. What they don’t have are the many cracks and imperfections that brittle emeralds acquire when they’re formed in nature. Because of this, they tend to fluoresce more under ultraviolet light than regular emeralds do. Collectors, perversely, also often complain that synthetic emeralds are too clear and too perfect, and therefore fake-looking. But what else could anyone expect from something baked on platinum in a gold oven?
Rubies and Sapphires
Rubies and sapphires are the same, except for the trace amounts of coloring minerals. Aluminum oxide crystals are sapphires. The most famous sapphires are blue, but they can be clear, yellow, green, or even pink. It takes a sprinkling chromium (always the chromium) to make the stone turn red and be called a ruby.
While emeralds had to be mined until the late 1900s, the first human-made rubies showed up in 1885. When a seller was found handing out rubies at far below market value people got suspicious. After some investigation, the gems were found to be real rubies, but clearly ones that were made, not mined. What no one could figure out was how their mysterious creator had made them in the first place. This early alchemist worked magic and disappeared, taking their lucrative secret with them.
And nobody learned the secret of making synthetic rubies until 1970, when examination of the fake rubies showed that they were melted down powdered aluminum oxide with chromium added during the melting process. Modern rubies and sapphires are made in a furnace with a sort of washing machine detergent slot at the top for the aluminum oxide powder and coloring materials, a hydrogen flame in the middle, and a ceramic base piece. Gem manufactureres fire up the flame, and then engage an automatic hammer at the top of the furnace that tap taps the powder out of the slot and down into the flame. The flame melts the powder which drips and dries on the ceramic base. The boule, or the tube of sapphire or ruby, will automatically split in half when it gets put under pressure. Additives like chromium will make red rubies. Nickel will make yellow sapphires. Add the mineral you want to get the color you want.
Ruby is harder than steel, and so even though it suffers the same problems of ultimate clarity and perfection that emeralds do, the demand for them doesn’t drop. They’re used in industrial processes, and in optics. These gems aren’t just pretty.
Diamonds Made From Anvils and Oil
The most sought-after gems of them all, diamonds, turn out to be generally the most straightforward to make. Most of the time what’s needed is carbon and pressure. People create diamonds by exerting pressure with belt presses. They do it by pressing carbon in a six-sided mold and using six hammers to make cubes like dice. They lock successive molds in a barrel and fill the barrel with oil. When they heat the oil, it expands and puts pressure on the molds inside, until they make a diamond. Anything that puts a lot of pressure on a little carbon will do.
A more subtle way of making a diamond is to fill the air next to a diamond-covered surface with a hydrogen and hydrocarbon vapor. The diamonds that are already present act as seeds, encouraging other diamonds to grow by precipitating out of the hydrocarbon vapor.
Still, there’s no guarantee that the rich will get richer without the all-important hydrogen vapor. It forms highly reactive kind of hydrogen, that is necessary for weeding out intruders in this garden of diamonds. Two things can grow on the diamonds already there; diamonds and graphite. Diamonds can’t get worn away quickly by the reactive hydrogen. Graphite can, and does, leaving a diamond surface to be built up and built up by more diamonds.
Diamonds made by humans at first came out a yellow or brown color, so that natural diamond sellers didn’t consider them a threat. Since then, synthetic diamond makers have discovered that the discoloration have found that the yellow came from nitrogen impurities, and high-end makers eliminated it. They also found that adding boron made blue diamonds, and irradiating the concoction made pink diamonds. Suffice it to say, that the miners aren’t laughing anymore, and are finding ways to thwart the makers. One of the highest-end machines designed to tell the difference between constructed and mined diamonds is made by De Beers. What the miners don’t need – despite extreme bad press for them – is any argument for why people might care whether their diamond was dug from the ground or made in a lab. The world over, people prefer “natural” stones despite them being smaller, with bigger flaws, and more expensive. Every site selling lab-grown gems of any kind takes pains to explain that most jewelers can’t even tell the difference. The alchemists have finally won. Now they just need a good publicist.
Source: http://io9.com/5938744/acid-and-gold-the-modern-alchemy-of-artificial-gemstones
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