In the past I used a dSLR and used a small flashlight to shine through the viewfinder to get a spot of light when the subject is in focus. Then if you know where on the piece the crystal is, you can move your piece and easily find the subject.
Now with mirrorless this is no longer possible because the viewfinder is just a small LCD.
It's a bit of a long shot, but who has a creative idea to get a beam of light out of your objective so it focuses to a spot at the focal point? It would make life much easier for me. Or another creative idea, like projecting a grid on the specimen that you can use to find your crystal? Ideally a color gradient grid so you know where you are

Love to hear crazy ideas
