Diamond Fingerprinting

He was wearing aviator-style sunglasses with dark gray lenses, but otherwise was beige from head to toe. Even though the year was 1993, Beige Man was wearing a beige leisure suit otherwise identical to the mustard one my high school physics teacher wore in 1977.

His skin was beige. His hair was beige. I’ll be darned if his expression wasn’t beige, too. The guy was nearly invisible except for his light-brown briefcase, its color striking in contrast, nearly a whole pixel removed on the RGB scale from beige.

Beige Man had made an appointment three weeks previous, but was vague about what type of samples he was bringing, or what he was hoping to learn. He came from the NSA, a notoriously secret federal government agency.

I ran the demo lab at Park ‘n’ Park. Actually, I was the demo lab. And also the customer service group and the newsletter creative and production team. I wrote the operating manuals, articles for trade journals and a textbook chapter or two. But that day, I was the demo engineer, and Beige Man was the prospective customer.

My actual job title was Analytical Products Manager. It was a small company, and we were making it up as we went along. I thought it was an okay title, except when the CEO would abbreviate it as Anal Prod Man on the org charts he drew on the blackboard. English was not his first language.

I greeted BM with a smile and a handshake, introducing myself. He returned the handshake, but my smile was fully absorbed into the straight line of his thinly lipped beige mouth. He took my business card but didn’t give me one in return.

BM removed his sunglasses as I led him out of the lobby into the adjoining lab, and he blinked a few times in the fluorescent light. His eyes weren’t beige; they were completely colorless. I looked away. Took a deep breath.

Don’t worry: There were other people around. They just weren’t in the lobby or the demo lab. I wasn’t that frightened, not really, not all that much. Skeeved is a better description. A teeny bit repulsed.

I was wearing a silk blouse and a light wool jacket with matching skirt, no doubt in some ridiculously bold color like navy. Pantyhose and low heels completed the outfit. That’s what we wore back then, folks, in a customer-facing job. Anyway, it was good that I had long sleeves to cover the goose bumps.

Do it for the story, Mom, Max would have said, but he was still in heaven, playing golf with God, according to the story he related when he was a toddler. Weird: I’m pretty sure none of us had mentioned God, heaven—and for sure not golf—at that point in his life. Golf had no place in our lives, and still doesn’t.

Do you mind if I close the door? Beige Man asked politely. I don’t want other people overhearing us, he said.

Before our meeting I had signed a non-disclosure agreement, along with the CEO. BM didn’t want information about his project getting out. And I’m not concerned about violating that NDA now, because—well, you’ll see.

I agreed to the closed door. No one staffed the lobby, on the other side of the door, but the demo lab had another door that led to the manufacturing floor, and I’m sure people would have heard me scream. And don’t worry, it’s not that kind of story.

It was time for BM to reveal the purpose of his visit. Steel yourself. He unlocked the latches of his light-brown briefcase, angled it open, and removed a small plastic case containing a diamond. A gem-cut diamond. Pretty good-sized one, too, maybe a carat.

Carat, caret, carrot.

BM spoke quietly in an inflectionless voice, enunciating just enough to make himself understood the first time. I’m looking for a technique that can identify an individual diamond, even if it’s been re-polished or re-cut. I’m hoping your new technology can do that, this atomic force microscope.

Clearly he hadn’t read any of the literature on atomic force microscopy. No chance, BM, no chance.

I woman-splained gently, AFM is a surface technique. An extremely-sensitive surface technique, to be sure, but it doesn’t look inside a diamond at the atomic structure. You’d need to see inside to find unique characteristics. A flaw, like missing carbon atom or a carbon atom shifted out of position. Or an impurity: a different type of atom occupying a carbon site in the crystal lattice.

AFM can scan the surface in great detail, I continued. But since a diamond can be re-polished or re-cut, the surface is not where you are going to establish the diamond’s identity. I’m awfully sorry you made the trip.

Beige Man’s face betrayed not a flicker of regret or annoyance or despair that he had traveled across the country without having spent sixty seconds looking up what an AFM could actually measure.

To cheer him up in case his blank expression hid any emotion at all, I said, Let’s do a quick scan anyway, and I’ll show you. I donned gloves, took the diamond, cleaned it in isopropyl and mounted it on the sample stage. His colorless eyes tracked my every move. Sure enough, the surface was flat. Nearly planar, though we did see a couple of atomic-height steps where the polish was oh-so-slightly misaligned with the crystal planes. Now, I think that’s cool, but BM was flooded with disinterest.

I printed the scan on the attached printer. Took me a few seconds to decide between applying a muted gray-scale to show the atomic step, or something in orange with an iota of blue mixed in, diluted to match BM’s leisure suit. I chose the latter and handed the print to him.

He said, Would you please delete that file? I nodded, and deleted it in front of him, so he could feel safe.

Beige Man put the diamond back into its case and relocked it inside his light-brown briefcase. I walked him to the lobby, and nodded our good-byes. I knew better than to go for a second handshake.

He didn’t have to sign out, because he hadn’t signed in.

[Top photo is not BM's diamond, of course not, but instead another form of carbon: graphite. Graphite has that handy layered structure that makes it good for calibrating AFMs and also serving as pencil 'lead.' The height of those steps you're looking at is 0.335 nanometer. Isn't that cool? Also, the photo is edited by me, deliberately beiged and blurried to match the story line.

Bottom photo is me in the demo lab, back in the day, wearing my customer-facing togs with the first Park 'n' Park AFM behind me. There is a serious version of this photo somewhere, but you get the idea.]