Haggy,
Glad my quick explanation helped, though you might follow the link to discover ways to reduce the image size.
I like the look of the silica inset, and can see why you like it. Is it always that colour or does it come in or can you tint it other colours?
As far as using epoxy goes, start a thread asking for advise, we have a few turners who do very well with the stuff. You never know, you might offer up some ideas they can use as well.
As to what type of plastic I've acquired, nope no idea. As a guess I'd say it was a thermoplastic like the stuff normally used in injection moulding machines.
And as for showing your pupils anything from the site, the AWGB exists to promote Woodturning, one of the committee will give you 'Chapter & Verse' but not only would there not be a problem, but I'l warrant that the nearest club would assist you, if you asked.