These are lab created sapphires which were grown for use as a sensor window in the F35 fighter jet but didn't meet spec.  They've been faceted and are available as loose gems! Note that the calibrated cuts have a bit more size variation than usual, up to a quarter mm. These stones glow blue under shortwave UV because of titanium contamination.This is a really cool material--lab sapphire grown for windows on the F35!  These aren't used on the cockpit but on a sensor array right below.  There are numerous sensors on the bottom of an F35 that allow for a 365 degree view in a wide spectral range.  With the incredible accelerations and speed that have to be withstood an ultra hard, ultra durable material like sapphire is needed.  But how do you make giant, flat sheets of sapphire?  Normally you'd cut windows out of a big round boule grown by HEM or kyropolis but the shape really isn't conducive to larger flat shapes. To solve this problem Rubicon, at the time one of America's greatest sapphire growing companies, got a 5 million dollar grant to develop the LANCE furnace, an ultra high tech crystal growing machine that grows the world's largest flat sapphires via the "boat" method aka HDSM.  If you've ever been to a Quiznos think of the ovens with a conveyer belt they use to toast subs evenly--it's basically that but with a giant flat pan of molten, crystallizing sapphire. Though the LANCE is absolutely incredible (we got to see it in person and meet the head crystal grower!!) it didn't have a 100% success rate, and over time the company built up a pile of defective sapphire crystals that had either been contaminated with titanium (which turns them pink and ruins UV transmission), developed bubbles, shattered during growth or usually all three.  They recently closed their factory in Chicago and auctioned off the contents, and we were able to buy the entire pile of defective crystals!  It was a dream come true!1023