Tanzanite, December’s birthstone, is found in the shadows of the majestic Mount Kilimanjaro in Tanzania, the only commercial source for the gemstone.

Turquoise, the December birthstone, has a distinct blue or greenish-blue color because it contains copper, and is most commonly found in China and the U.S. southwestern states Arizona, New Mexico, Colorado and Nevada.

Topaz, November’s birthstone, is a mineral species that naturally occurs in a range of color, including various reds, pinks, purples, yellows, oranges, browns, and more rarely, pale blue. Topaz in yellow and reddish brown are commonly heated to create more desirable pink gems.

November’s birthstone, citrine, comes in the colors of citrus fruits, ranging from deep reddish orange, reminiscent of Madeira wines, to pale and saturated yellow hues. In fact, its name is derived from the French word “citron,” which means “lemon.” Citrine’s optimistic colors bring to mind the warmth of mid-day sunshine.

Tourmaline, the October birthstone, comes in almost every color of the rainbow. The most popular varieties range from rich reds, pinks and peach colors, to emerald greens and yellows, to blues and violets.