I've run a lot of laser diffraction experiments with nothing more than a quality laser pen, some rasor blades, a human hair and a small hole in a Christmas card as demonstrations for laymen but I'm kind of bored with these now.

I'd really like to emulate X-ray crystallography diffraction, in a backyard lab setting but found it hard to get (Google) some information on that.

One possibility is to construct a macroscopic $\text{NaCl}$-style lattice from copper single filaments, with a $d$ of about $0.1\,\mathrm{mm}$. That would of course not be easy to pull off but not impossible either, IMO.

I do have another idea, which I want to keep 'under wraps' for now because I'll be test driving it shortly. 

Searching P.SE for 'laser diffraction' I came across one intriguing comment claiming  $\text{XRD}$-style laser diffraction may be possible with *synthetic Opal*. Googling then threw up large amounts of links to applications of laser diffraction in the field of particle characterisations (something I'm not interested in for now).

And then there's a paper titled *Linear and Nonlinear Optics of Synthetic Opal* by *M. V. Vasnetsov, V. Yu. Bazhenov, V. V. Ponevchinsky*, which throws a little light on the structure of (a) synthetic Opal: [![the structure of one synthetic Opal][1]][1]

But with a lattice $d \approx 100\,\mathrm{nm}$ it isn't clear how such a material could exhibit *'laser $\text{XRD}$'*.

Commercial synthetic Opals are not expensive and readily available but the samples I've seen are all either non-transparent or transparent like glass, so it's hard to see how they could produce the effect I'm looking for.

A beautiful (commercial) sample of synthetic Opal (about $8\,\mathrm{g}$):

[![Opal][2]][2]

The fascinating coulours of Opals are attributed to diffraction.

Does anyone here have experience/information on laser $\text{XRD}$ with Opal or anyother substrates?


  [1]: https://i.sstatic.net/djAIv.png
  [2]: https://i.sstatic.net/W2L3W.jpg