Sapphires

I recently completed an article on Montana sapphires for Distinctly Montana Magazine, focused on beautiful gems from Yogo Gulch. But sapphires have practical uses too.

Because rubies (red) and sapphires (famously blue, but also pink, yellow, green, purple, and even colorless) are nothing more than corundum, aluminum oxide, with some interesting trace elements (mostly titanium and iron), they are very hard—number nine on the Mohs Hardness Scale, second only to diamond. Consequently they find their way into watch and clock bearings, and those that don’t make the cut as gems are sometimes used as high-quality abrasives.

The first lasers, in 1960, used synthetic rubies to focus light into a coherent beam. Solid-state integrated circuits sometimes use sapphires formed into small thin wafers as their insulating substrate. Larger sheets built from synthetic sapphire sometimes make tough windows in armored vehicles, as well as mundane surfaces such as grocery-store barcode scanners where scratch resistance is valued. High quality watches may have sapphire crystal faces in addition to gem-like bearings inside.

Even though Auguste Verneuil invented a process for making synthetic sapphires in 1902, natural sapphires were used for non-jewel applications for decades after that. Today about 250 tons of synthetic sapphires supply the world annually with watch bearings, abrasives, and specialty uses. The US and Russia manufacture most synthetic stones, while Madagascar is the leading gem sapphire producer.

Watch for the article on Montana’s Yogo sapphires in the Summer issue of Distinctly Montana.

Image: The 182-carat Star of Bombay star sapphire, via Wikipedia.