Asw a grad student, I used to grow my own laser crystals from scratch. I also used to “cut” them the same way they cut diamonds. So one day, I decided to go to the Diamond District in New York City (48th street between 5th and 6th avenues) to ask the diamond cutters how they did it.
A very interesting experience. You’ve never seen such a paranoid group in your lives. Military bases don’t have guards this paranoid. Of course, they have good reason – diamonds are extremely small and extremely valuable, easily snatched, and worth the trouble of stealing. So there are cameras and guards everywhere. Doors are double-locked, requiring key and keycard for entry. Secretaries sit behind thick sheet of bullet-proof glass.
Every time you walk into a room, all eyes swivel to you. In a world where everyone knows everyone else, the Stranger is intensely distrusted.
Nevertheless, I walked into this with an open and innocent attitude, and got bounced from person to person. I eventually talked to a diamond-cutter – but only over the telephone. There aren’t a lot of diamond cutters, and they tend to keep it in the family. Also, with the rise of especially hard abrasives, it’s easier to grind diamon than to cut them precisely. I eventually found some books on the topic in the next street over.
If you want to learn how to cut crystals, you can get he information for free from companies that grow them. The sam basic principles apply to softer, more common crystals as to diamonds. I learned from the former Harshaw company, but they’re part of someone else these days. You can cut many common crystals with razor blades, or with lathe tools ground to a fine edge. My advisor used to cut extremely thin sections using a doubleedged razor blade. I myself destroyed an entire crystal boule earning how to cut samples, but eventually got good enough that I could simply “cut” the crystal ends and use them in the laser cavity without polishing.
The trick is to align your cutting edge with the “clavage planes” of the crystal. In the case of alkali halides (like table salt) and alkaline earth chalcogenides (like Mag Fluoride) the planes are utually perpendicular and parallel to the faces of the rectangular crystals. You simply place the edge of your razor blade or cutter along the ceavage line and strike with the hammer.
Diamonds are more complex – the cleavage planes are more compliated. To kep the diamond stead it is mounted on a “dopping stick”. A small notch or “kerf” is abraded along the cleavage line, a cutting tool is inserted, and (as with the softer crystal) it is smartly struck. If all has ben done properly, the crystal will fracture neatly along the cleavage plane. If not, the crystal will shatter irregularly.
There s a distinction between ardness and brittleness – a diamond is very hard, and will cut glass, and won’t be scratched itself by any natiural materials. But you can cleave a diamond along its cleavage plane with a steel tool, which is actually softer than diamond. t will eventually wear away (I used to change razor blades every ime to make clean cuts in much softer crystals)., but it’s nt as if the diamond ruins the tool after every single cut.