Aluminum, Sapphire Glass, and the Periodic Table of DEATH & Mystery

When you saw Aluminum (Al), I bet you figured I’d write about aluminum foil, invented in Switzerland in 1910 and first used in the U.S. to wrap candy in 1913 (1). Or its innovative use in the construction of the Empire State Building in New York City (2). Or I’d write about how the best American Christmas TV special ever, A Charlie Brown Christmas*, pretty much single-handedly killed the Aluminum Christmas tree (3).

Red, Green, and silver Hersheys Kisses in a pile — Hershey, PA, USA – December 10, 2015: Foil wrapped Hershey s Kisses in Christmas colors on display in ChocolateWorld.

But you’d be wrong.

Instead, I’m going to write about Transparent Aluminum. And yes, it’s a real thing, not just made up for Star Trek IV, The Voyage Home (4) as a bargaining chip for 6-inch plexiglass.

It turns out Aluminum (Al), atomic number 13, is very lightweight, very malleable, easily recycled, the most abundant metal in the Earth’s crust at 8.1% (5) and is the third most common element after oxygen and silicon (6). But it’s rarely found in pure form, and that’s where we start, with a mixture of Al and oxygen: Al₂O₃—Aluminum oxide, more commonly called corundum (7). It’s even better known as rubies and sapphires (8). Yes, the gemstones. The ones in rings and earrings and necklaces. In rubies, the red color comes from a contaminant of chromium (Cr). In sapphires, the blue color comes from contamination of the Al₂O₃ with titanium (Ti) and iron (Fe). Get rid of the contamination, and Al₂O₃ is clear and transparent.

Satellite in space over earth and samples of sapphire glass — Venmark International Keeping your products in front of the World

One property of transparent Al, or “sapphire glass”, is incredible hardness, a 9 out of 10 on the Mohr’s hardness scale—only diamond is harder (9, 10)—which makes synthetic Al₂O₃ particularly useful for scratch-resistant optics, lasers, windows in satellites and on spacecraft, and for military applications, like body armor (11).

So, this post is actually about how transparent Al can be the difference between life and death in places like the battlefield, because it turns out synthetic Al₂O₃ can be made into windows that will not only stop a bullet, but will pulverize it (12, 13). Transparent Al “glass” is lightweight, thin, abrasion resistant, and won’t spiderweb with a bullet’s impact. Made into windshields for Humvees and MRAPs, and in the windows for the international Space Station, transparent Al protects the men and women of our family who volunteer for some of the most dangerous work on earth and in space.

Signs Book Cover with the face of a giant ape staring at the reader and a ghostly tech hand to one side — Signs: A De-Extinct Mystery Book 2

Why did I suddenly decide to write about transparent Al? Because transparent Al will stop a 50-caliber bullet while plexiglass can’t at close range. *Shameless plug* This will become very important in book 2 of the De-extinct Zoo Mystery series, SIGNS. On sale now at online booksellers.

Song(s), Book, and Movie? The first song is easy for the space aspect: Space Oddity (original release 1969; the linked recording is the 2015 Remaster) by David Bowie. I love David Bowie. And, of course, an 80’s hit, Major Tom by Peter Schilling. 4-3-2-1 …

Movie: Mighty Joe Young. Not he 1993 version where Charlize Theron continually shrieks “JOE! JOE!“. The 1949 version because the size of Joe Young is about the size of the Gigantopithecus blacki in Signs (2023). Click the link and see what I mean. It was one of my sister Paula’s favorite as a kid.

As always, these are my own opinions* based on my biases, knowledge, and understanding, and the websites I’ve linked are in no way an endorsement. Although I have to admit, transparent aluminum is pretty cool.