In my early personal history * –
There is a special place to Geology in general and making transparencies Working at the Geologic Department of Geology at the Hebrew University (This is actually the only job I would go to in the morning with a song in the heart).
The process begins from a rock sample like this- in the first picture.
In order to makes the slide I cut a stone slice, like in the second picture..
Transparency – is a piece of stone like this: