September Birthstone Color: A Tale of Two Blues

The Many Shades of Blue in Sapphire

When people think of the color of September's birthstone, most picture a clear, brilliant blue—often the kind found in classic sapphire jewelry. Yet, sapphires actually span a colorful spectrum. The typical blue sapphire can range from a soft “sky-blue” to the vivid “cornflower blue,” and even deeper, richer royal blue tones.

These shades are more than just beautiful—they reveal the sapphire’s very nature. Trace elements like iron and titanium combine to produce the classic blue, while vanadium can inject a hint of violet. Some sapphires are breathtakingly clear and bright in daylight but shift to a purplish or reddish tone under indoor lighting—an intriguing phenomenon called color change. There are even star sapphires, where needle-like rutile inclusions create a star-shaped glow (asterism) when the stone is properly cut and lit.

Another fascinating feature is color zoning, where areas of differing shades naturally develop within a single stone. Cutters aim to position the most desirable color zones face-up to maximize visual appeal. Sapphire can also exhibit pleochroism, meaning it may appear greenish-blue from one angle and violet-blue from another, depending on how you look at it.

For many, the ultimate expression of the birthstone color of September is the rare and velvety cornflower blue seen in Kashmir sapphires. These gems, mined in the late 1800s, are prized for their depth, clarity, and gentle inner glow—so rare that they now fetch top prices at auctions.

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Lapis Lazuli: A Deep, Ancient Blue

Contrasting with the transparent sapphire is lapis lazuli, often acknowledged as an alternative September birthstone. Rather than a pure mineral, lapis is a metamorphic rock consisting mainly of lazurite, with specks of pyrite and streaks of calcite embedded in it.

Its color is nothing short of striking. The deep, opaque blue arises from the presence of sulfur-based radicals—particularly the trisulfur (S₃) radical anion—within its crystal structure. These molecular components absorb specific light wavelengths and reflect pure, intense blue.

What gives lapis that almost magical appearance are the golden flecks of pyrite, which contrast with the velvety blue, and the white swirls from calcite, which soften and highlight the hue. The exact shade of the blue color of this birthstone for September depends on these proportions: more lazurite deepens the blue, more calcite lightens it, and the pyrite adds sparkle.

This deep blue has been prized since ancient times. It was ground into ultramarine pigment for painting, even exceeding the value of gold during the Renaissance. Lapis appeared in the earliest jewelry and artifacts discovered across ancient civilizations.

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Fancy Sapphires: A Rainbow Beyond Blue

While we usually associate sapphire—and by extension September's birthstone color—with blue, the corundum family actually displays almost every color except red. Once corundum turns red because of chromium, it becomes known as a ruby, so all non-red gemstones in this family are classified as sapphires, including those in pink, green, violet, yellow, and beyond.

Let’s look at a few examples:

• Yellow sapphires range from pale lemon to warm gold, colored by iron. Sri Lanka is known for particularly clear, richly hued varieties.
• Pink sapphires draw their shades from chromium—the same element that, in higher concentrations, produces ruby.
• Orange sapphires and the extremely rare padparadscha blend orange and pink tones—a sunset captured in stone.
• Green sapphires emerge from combinations of iron and vanadium and can appear soft or forest-hued.
• Purple or violet sapphires reflect combinations of chromium, iron, and titanium for a regal palette.

Specialty types like parti-colored, bi-colored, color-change, and star sapphires add even more diversity to the conversation around September birthstone colors.

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