September Birthstone: Sapphire
Sapphire is corundum, ruby's mineral, in every color except red. The blue is the legend: the stone of medieval royalty, of clerical rings, and of the most famous engagement ring in the world.
For buyers, sapphire may be the most complete package in colored stones: superb hardness, rich colors, wide price range, and a healthy supply of honest material at every budget.
The blues, and everything else
Fine blue sapphire is a velvety medium-to-deep blue with strong saturation; cornflower and royal blue are the trade's benchmark descriptions. Stones too dark go inky, and steely pale stones lose the magic.
Beyond blue, fancy sapphires cover pink, yellow, green, purple, white, and the rare orange-pink padparadscha. Teal sapphires, blue-green bicolors mostly from Montana and Australia, have become modern favorites for engagement rings.
Treatment and honesty
Most sapphires are heated, a stable and accepted treatment that improves color and clarity and should simply be disclosed. Unheated stones with fine color command large premiums and deserve lab reports.
Be wary of diffusion-treated stones, where color is cooked into just the surface; they are inexpensive and must be labeled as such, because a repolish can lighten them.
Built for daily wear
At 9 on the Mohs scale, sapphire is the most practical colored stone for an engagement ring or any piece worn daily for decades. It shrugs off dust, tolerates ultrasonic cleaning when untreated or simply heated, and holds a polish for a lifetime.
Buying notes
- Set your color target first: classic blue, a fancy color, or teal. Price varies widely by color.
- Medium tones show color in all light; very dark stones only perform in bright light.
- Eye-clean is achievable at most budgets; visible inclusions should mean visible discounts.
- Lab-created sapphire is real corundum with excellent color at gentle prices, ideal for hard-wearing jewelry.
Common questions
Is sapphire a good engagement ring stone?
The best colored option there is, in our view. Hardness 9, every color, strong tradition, and meaningful savings versus diamond at the same visual size. Our ring builder can price sapphire options directly.
What is a star sapphire?
A sapphire with oriented silk inclusions cut as a dome, showing a six-ray star that glides across the surface. Fine stars with good color are collectible; grayish commercial stars are affordable and charming.
