How do I include a birthstone in an engagement ring?

Last March a woman named Rachel walked in wanting to know how to include a birthstone in an engagement ring without making the whole thing look like a class ring. Her birthday is in September, so she'd assumed the center had to be a sapphire. She'd also read somewhere that hiding a birthstone under the setting brings good luck. The problem was the stone she'd picked for the hidden part, a pale blue topaz from her mother's ring, which wasn't going to survive fifty years of daily wear in a prong setting.

Where the stone sits

You've got four real choices: make the birthstone the center, put it in the gallery under the main stone, add it as a small side stone, or set it inside the band where only you know it's there. Each has tradeoffs. Not all birthstones can take daily wear on the top of a ring. I tell clients that flatly.

Side stones are the easiest way to include a birthstone in an engagement ring if the center is already a diamond. A three-stone ring with a round brilliant center and two small colored stones, maybe 3mm each, is a clean look. I built one last year with a 1.04 carat F/VS1 round in the middle and two 4mm Montana sapphires on the shoulders. The client, Daniel, wanted his partner's September birthstone without giving up the white diamond sparkle. It worked.

The hidden approach is the one I like most. A small colored stone set in the gallery under the center, or a tiny stone set flush into the inside of the shank. Under the gallery you can actually see it when the ring is off. Inside the shank, only the wearer knows it's there. This works for any birthstone, including opal and pearl, because those stones sit protected from knocks and wear. A flush-set 2mm stone inside a band usually adds about $175 to $250 to a custom job, depending on if we cast the band around the stone or cut a seat into an existing one.

What actually holds up

April's diamond, July's ruby, September's sapphire, and June's alexandrite are all fine as a center. May's emerald can work in a bezel if the wearer is careful, but it's brittle and most emeralds are heavily oiled, which means chemicals and ultrasonic cleaning can damage the stone over time. October's opal and June's pearl are off the table for a daily-wear center. Opal contains water and will craze with temperature swings. Pearl is a 2.5 on the Mohs scale. A ring worn every day will scuff it within months.

Stones I'd never set as a full-time center in an engagement ring:

• October opal (Mohs 5.5, water-bearing)
• June pearl (Mohs 2.5 to 4)
• December turquoise (Mohs 5 to 6, porous)
• August peridot (Mohs 6.5, brittle in thin corners)

When you do use a colored birthstone next to a diamond, think about the metal color. Yellow gold warms up a blue sapphire and makes an emerald look greener. White gold or platinum next to a pale aquamarine can wash it out. I usually suggest 18k yellow for colored centers, unless the client is set on a white-metal ring. Then a slightly deeper colored stone compensates.

The process and the honest take

A few years back a client, Priya, asked for an opal to be set as the center of a bezel engagement ring. I told her no for daily wear, and she pushed back. We compromised on a diamond center with a small opal hidden in the gallery, plus two tiny lab-grown emeralds on the shoulders for her partner's May birthday. She wore it for two years and came back for a cleaning. The opal had a hairline fracture from a fall, but it's hidden, so it doesn't matter. Had that opal been the center, she'd have been in tears and I'd have been replacing a stone three times.

The custom process for adding a birthstone isn't complicated if you're already building the ring from scratch. At the CAD or wax stage, the jeweler should show you exactly where the stone sits and how much metal surrounds it. A hand-fabricator might pierce a small hole in the gallery and set the stone flush. Expect the whole custom ring to run six to ten weeks, first consultation to final polish. A hidden birthstone detail usually adds $150 to $400, depending on the stone and whether it came from a lab or the ground.

My honest take: include the birthstone if it's durable and you want it visible. If it's soft, hide it. If it's a birthstone only because tradition says so, skip it and choose a stone color you actually like. I've had clients pick a garnet because January, only to realize they hate red. That's a bad reason to build a ring around a stone.

Bring the stone to a bench jeweler and ask them to set it flush. You'll know it's there.