It’s easy to make a ruby at home or in a workshop. Here are two easy methods for making your own homemade ruby gemstones.
About Ruby and Sapphire
Ruby is the red crystalline form of corundum, which is commonly called sapphire. Pure sapphire is pure aluminum oxide (alumina, Al2O3) and is colorless. Trace amounts of chromium (Cr) turn the gemstone red (rubies), while adding titanium and iron turn the crystal blue (blue sapphire). In all forms, corundum has a Mohs hardness of 9. The crystals make beautiful, durable gemstones that have a stable color.
Method #1 – Make Ruby Using an Arc Welder
Making rubies with an arc welder is surprisingly quick and effective. You can make large polycrystalline gemstones this way. The ingredients are aluminum oxide (alumina, Al2O3) and chromium(III) oxide.
- 99 grams alumina (Al2O3)
- 1 gram chromium(III) oxide
- Arc welder (carbon electrode recommended)
- Graphite crucible
Alumina is a readily available, inexpensive abrasive. Amazon and other retailers sell chromium(III) oxide. This is a green powder. Unlike its hexavalent cousin, chromium(III) is safe to work with.
Find inexpensive carbon electrodes for an arc welder online. Graphite crucibles are also available online, or (because graphite is very soft) you can scrape a depression into any sufficiently large chunk of graphite. Just keep in mind, the final shape and size of the ruby depends on this depression.
- Stir together the alumina and chromium(III) oxide to make a homogenous mixture. You want 99% alumina and 1% chromium oxide, so you can adjust the recipe as needed. For example, you can use 49.5 grams alumina and 0.5 grams chromium oxide.
- Pour the mixture into the depression in the crucible.
- Turn on the arc welder and fuse the powder into ruby.
Use care removing the ruby so you don’t burn yourself. Shine a black light or other ultraviolet lamp on your creation. Ruby fluoresces at 694 nanometers (red), enhancing the brilliance of the gem.
That was easy, right? There is an even faster method of making ruby.
Method #2 – Make Ruby Using a Microwave
Making rubies in your microwave takes a whole 10 seconds. Intense heat from plasma fuses the ruby. But, don’t use your kitchen appliance for this because (a) vapors may linger and (b) making plasma in the microwave risks breaking the oven. Proceed if you have an extra microwave sitting around that you don’t mind damaging.
- 99 grams alumina (Al2O3)
- 1 gram chromium(III) oxide
- aluminum wool
- Study glass dish with a depression
- Glass cover
- Black light (optional)
The starting materials are exactly the same as for the arc welding method. You want a mixture of 99% alumina and 1% chromium(III) oxide. Also, you want aluminum wool to generate plasma in the microwave. Aluminum wool is an abrasive and a common air filter material. For the study glass, options include the depression in a thick glass candlestick holder or a shot glass. For the glass cover, consider a watch glass or inverted saucer. Use borosilicate glass (e.g., Pyrex), if available, because it handles heat well. The cover contains the plasma produced within the container. If the plasma gets free, it can travel throughout the microwave and damage it. The black light is for detecting ruby fluorescence.
- Combine the alumina and chromium(III) oxide.
- Pour the mixture into the depression in the heavy glass.
- Add a few aluminum wool fibers. You want a bit of aluminum dipping about halfway into the powder and whiskers extending above the powder.
- Cover the container with a second piece of glass.
- Hit 10 seconds on the microwave and turn it on. Expect a scary bright light and possibly some crackling sounds.
- Don’t burn yourself removing the ruby. A black light reveals the pretty fluorescence.
Tips and Safety
- Alumina comes in a variety of particle sizes. It doesn’t really matter what you use, but finer particles have more surface area and melt more readily.
- Consider the purity of the alumina. If it contains any sodium, the ruby becomes opaque. These rubies are polycrystalline anyway, but if you want a translucent ruby, only use alumina of at least 99.9995% purity. Usually, this is alumina not made using the Bayer process.
- Alumina and chromium(III) oxide aren’t the worst chemicals to work with, but you don’t need to go around inhaling them. So, avoid dust exposure and wear a mask. Obviously, wear protective goggles if you use an arc welder.
- Freshly fused ruby is extremely hot. The crucible or glass holding the ruby is similarly hot. Use oven mitts, at a minimum.
- If you use the microwave, expect glassware breakage. Thick glass survives the heat better than thin glass, but uneven heating still results in cracks. Also, if the glass breaks during the microwaving process and looses the plasma, appliance damage is possible.
These potassium ferricyanide crystals aren’t as durable as ruby, but you don’t need heat to make them either.
How Rubies Are Made Commercially
If you buy a synthetic ruby gemstone or use a ruby laser or maser, your ruby will have been made using a slightly different method than you use at home. Gaudin made the first synthetic rubies in 1837 by firing potash alum with a bit of chromium. The Verneuil process (1903) became the first commercial method of making rubies, which fuses BaF2, Al2O3, and bit of chromium with red-hot heat. Using an arc welder or microwave is an adaptation of Verneuil’s process, just with different starting materials. Other methods include the Czochralski process, flux process, and hydrothermal process.
- Feigelson, Robert (2004). 50 Years Progress in Crystal Growth: A Reprint Collection. Elsevier. ISBN 9780080489933.
- Hughes, Richard W. (1997). Ruby & Sapphire. Boulder, CO: RWH Publishing, ISBN 978-0-9645097-6-4.
- Matlins, Antoinette Leonard (2010). Colored Gemstones. Gemstone Press. ISBN 978-0-943763-72-9.