I checked around on the internet and found several sites where others have been doing the same thing. The best part was that everything I'd need were pretty common household items. So, I rounded up the necessary supplies and began imagining how great life would be once I'd cornered the international diamond market.
Step 1: Materials
A standard home microwave oven
2 coffee mugs
3 pieces of 3mm graphite pencil lead
A few drops of extra virgin olive oil
A 5" piece of 100% cotton thread
The hardest item to find was the 100% cotton thread. It's amazing how scarce that stuff is. After searching through all of our sewing notions, I finally found some black thread that I think my mom bought back in the 70's.
Step 2: Prepare the Olive Oil
Place a few drops of olive oil onto a plate and lay the thread in the oil. The thread will absorb some of the oil.
Step 3: Transfer Oil to the Graphite
Don't pull the knot all-the-way closed!
Carefully slip a piece of graphite through the knot loop and lay both the thread and graphite on a plate. I used two halves of a toothpick to keep the graphite suspended above the plate. This helps keep the oil confined to a single spot on the graphite.
Pull both ends of the thread until the knot has closed around the graphite.
Wait about 30 minutes for the oil to soak into the graphite.
Step 4: Setup (i.e. clean) the Microwave Oven
I assured her it wouldn't, and that I'd need to clean the microwave before my "experiment." This ended her objections.
So, while the oil was soaking into the graphite, I cleaned the microwave. The sites I'd read from others folks doing this insisted that a clean microwave would yield better results. Maybe, maybe not, but it sure looks better.
Step 5: Remove the Thread
Try not to slide the thread up-and-down the graphite. Remember, it's important to keep the oil concentrated in one spot.
Step 6: Set the Graphite on the "Crucible"
Set 2 more pieces of graphite (non-oiled) on the upturned mug, parallel to each other.
Lay the oiled graphite across the other 2 pieces.
Place the other coffee mug over all of it.
Presto! It's a makeshift crucible!
Step 7: Place "Crucible" in Microwave
Step 8: Start the Microwave
Be advised: the microwave will spark a bit where the oil has soaked into the graphite. This is normal as the oil is bonding with the binder in the pencil lead. It should stop sparking after a few minutes.
After the microwave is done, let the mugs cool completely before removing them. Remember, if done correctly, you've generated 1,200+ degrees inside the crucible. Be safe.
Step 9: Admire the Finished Product
The oiled graphite will be broken. The others should largely be intact. You'll also find a small lump, slightly larger than a grain of sand where the oiled section was placed.
Congratulations! This is the product of your labors, a genuine diamond.
I took the raw diamond to a jeweler I know and had her test it. She confirmed that underneath the scale material, there's a tiny bit of diamond material. She said that its quality was pretty poor, but it did fluoresce like a "real" diamond.
Now, admittedly, this homemade synthetic diamond is too small and too filled with inclusions to make into jewelry. But, it technically qualifies as a diamond... and I made it, so that's pretty cool.
Step 10: Make it into a Keepsake
I filled a small washer with clear epoxy and dropped my diamond into it. After it hardened, I strung it on a chain to make a diamond necklace.
My wife was impressed. After all, how many women can wear a diamond that their husband actually MADE?