Names the gem tied to a birth month, so meaning is chosen before material.
Also called: gemstone, personalized stone
Measurement
Mohs 2.5 to 10, depending on the month
The basics
What to know about birthstone
A birthstone is an ordinary gem carrying an assigned month. The modern list American jewelers standardized in 1912 is the one most sellers use, and it has been amended since. Tanzanite joined December in 2002, and spinel joined August in 2016. Several months carry more than one option, and older, regional and astrological lists disagree with the modern one, so check which list a seller follows.
Hardness swings wildly across the twelve months, and that decides what the piece can be. Ruby in July and sapphire in September sit at Mohs 9 and handle a daily ring. Opal in October, at 5.5 to 6.5, holds water inside its structure and can craze. Crazing means a network of fine cracks appears after a temperature swing or long dryness. Pearl in June and turquoise in December are soft and porous enough to stain from lotion alone.
Emerald in May shows the trap most clearly. It tests 7.5 to 8, which sounds durable, but the crystal is full of inclusions and is nearly always oil treated. Heat and ultrasonic cleaning drive the oil out, and the stone looks worse than before. Check the specific month's stone against the piece you are buying. A pendant or earrings suit a soft birthstone, while a ring set with one will disappoint inside a year.
In photos
Birthstone on real products
See this option on different products. Open a photo for a larger view, or select the name to read its guide.
Birthstones are not a material, so they are made however their gem is made: mined from the ground, or grown in a laboratory. Tradition is what assigns them. The modern list was agreed by the national jeweler's association in the United States in 1912. It drew on much older sets of month stones. A committee has revised it a handful of times since.
Many affordable birthstone pieces use laboratory created versions of the month's gem, which is legitimate as long as the listing says created or simulated. Created sapphire and ruby have been in production since flame fusion was commercialized in the early 1900s. That history is why a bright created ruby costs a few dollars while a fine natural one costs thousands. Simulated stones are different again: a glass or a CZ in the right color, standing in for the gem rather than matching it.
Best for
When it works well
Personal gifts work because the choice carries a reason beyond taste.
New parents and milestone dates are well served, since a stone per child stacks naturally in a ring or a pendant.
Someone hard to buy for becomes easier, as the month narrows the decision for you.
Children's first jewelry often uses created stones, which keeps the meaning and lowers the cost of losing it.
