December Birthstone Color Depends on Which of Four Stones You Choose

December birthstone color is mostly blue, spread across four stones. GIA lists three December birthstones, tanzanite (blue to bluish purple), turquoise (blue to green) and zircon, which comes in many colors including blue. The Gem Society's birthstone chart adds blue topaz, the shade our December pieces use.

So if you're shopping for a December birthday, you've got room to choose. Whichever of the four she thinks of as her stone, it comes in a shade of blue, and the rest of this guide walks through each one so you can pick the shade that suits her.

The Four December Stones and Their Colors

Each December stone has its own shade of blue, and some come in other colors as well.

Tanzanite runs from blue to bluish purple. According to GIA, most tanzanite starts out as brownish zoisite and is heat treated to bring out its blue to violet color, and the Merelani Hills of northern Tanzania are the only place it's mined commercially.

Turquoise ranges from blue to green and is semi-translucent to opaque, often with veins of the rock it formed in running through it. The even, intense blue of the most prized turquoise has its own trade name, "robin's egg blue," GIA notes.

Zircon is the most colorful of the four. GIA lists red, orange, yellow, brown, green and blue, plus colorless. The Gem Society's chart lists it as blue zircon, and GIA notes that zircon is commonly heat treated to produce its blue.

Blue topaz is the clear, sparkling blue of the group. The Gem Society explains that most blue topaz comes out of the ground colorless or pale blue and is treated to give it a vivid color. Its shades go by names like London Blue (a dark, steel blue), Swiss Blue (a bright greenish blue) and Sky Blue (a pale blue).

They also differ in how they wear. GIA puts turquoise at 5 to 6 on the Mohs hardness scale and zircon at 6 to 7.5, and it recommends warm, soapy water rather than steam or ultrasonic cleaners for both.

Why Does December Have Four Birthstones?

December has more than one birthstone because there's more than one list. The traditional birthstones most familiar in the United States began in Poland between the 16th and 18th centuries, and in 1912 the National Association of Jewelers released a modern list. Jewelers have kept adding stones since, and tanzanite is one of the newer additions.

That history comes from the Gem Society's birthstone chart, which also notes that people in the United States now draw freely from both lists. Its December row lists blue zircon, blue topaz, tanzanite, turquoise and lapis lazuli across its modern and traditional columns. GIA names just three. That's why you'll often see four December stones, and five on some charts.

Blue Topaz or Turquoise for December

Both are December birthstones, so neither choice is wrong. Turquoise is on GIA's list, and the Gem Society's chart names blue topaz for December.

They differ most in how they look. Turquoise is earthy and opaque to semi-translucent, and it can lean green. Blue topaz is transparent, so it catches the light the way a solitaire does. If she wears a lot of sparkle, blue topaz will feel at home in her jewelry box. If she likes a softer, natural look, turquoise is her stone.

There isn't one "real" December birthstone. The best one is the stone she'll actually wear.

How We Make the December Birthstone

Our December pieces aren't mined blue topaz, and we'd rather you know that up front. They're set with a Swarovski crystal cut in a blue topaz shade, which gives you that clear December blue at a price that makes it an easy gift.

The solitaire birthstone necklace in December blue topaz holds a 1ct Swarovski crystal cut into a 6mm round, on 18k white gold plating over a brass base. It's hypoallergenic, lead-free and nickel-free, and it comes in a Cate & Chloe gift box. It's $39.99.