No cat's whiskers? No problem: use two razor blades instead.

Apart from being a touch on the dangerous side, this turns out to have other downsides. It's likely to create semiconducting junctions on both sides, or on the wrong side only, and this also greatly depends on the weight of the crystal.

It's a bit easier to swap crystals though, and rotating them to find good spots is simple enough.

More of a write up, and some curve plots from testing various minerals here:
https://cornish-semiconductor.com/index.php/Razor_blade_diode