We've all heard the stories. I think they perpetuate because people don't know what we really do, so I am going to take the mystery away.
The first thing I am going to tackle is stone switching. Everyone knows someone who knows someone who had their diamond switched. Frankly, I cannot imagine anyone walking in the door with a diamond worth more than my reputation. And that is what it would amount to, because trust is everything in this industry.
But wait, you say, what about the someone's cousin/aunt/poodle who got their stone switched?
Let's break it down.
A lot of it is urban legend- it makes for a good scare, and people love a good scare.
Some of it is honest confusion. I've worked for several jewelry companies over the years, and the corporate ones have quotas that their jewelers must meet while the sales staff make promises to buyers that the jewelers have to drop what they are working on to make happen, and you suddenly have three jobs strewn across your bench. That insanity is why I have a policy against 'rush jobs'. Everything is done in the order it is received.
Some of it is breakage or an undisclosed pre-existing condition or treatment. Yes, you can break a diamond. The cleavage planes are 9, it's how they can cut diamonds in the first place, and a Princess cut has you putting prongs down on four cleavage planes. Some diamonds have structural flaws- like a 'feather' that almost reaches to the surface, or a chip in the girdle where a customer hit it just wrong that increase the chances of breakage. And speaking of chips- I have seen chips and/or included crystals hidden behind prongs, many of them were stones in rings straight from the manufacturer. If the stone isn't oriented the exact same way when you reset it, of course it is going to look different, even though it is the same stone. Also, some treatments are not stable. I remember when Yehuda diamonds first hit the market. They would drill down into a diamond and bleach dark inclusions. Then they would fill the drill hole with a clear material and suddenly an I2 diamond looked great. They were marketed as clarity enhanced diamonds. It let a lot of people get a great looking bigger diamond for a fraction of the cost. Unfortunately, the filler they used for that drill hole would boil out when you were soldering on the piece, leaving you with a very ugly stone. The woman would be horrified and blame the shop, because her husband hadn't told her that he had bought a treated stone.
But a small portion of it is based in truth. There are dishonorable people out there. Know your jeweler, or if your jeweler has recently retired or you've moved, ask your friends who they trust. Look at online review companies like Yelp. Then go in and talk to the recommended people. Know your stone. Most jewelry stores have loupes or microscopes- ask the employees to help you use them to look at your stone. Every diamond has identifying characteristics- I once saw an inclusion that was shaped like a hummingbird. (That was amazing, btw) Have them use a diamond tester on your stone when you bring it in and when you pick it up to verify that it is a diamond. Double check for your identifying characteristics.