Reflective back gemstone

Suppose you had a high quality gemstone cab of a significant size.

And suppose it had a fancy cut bottom surface.

Then suppose you were going to bezel set that stone in a piece that
had a mechanical or very unattractive plate under the stone.

Now you wouldn’t want to view any of this through the stone, and
supposedly as long as the stone remains clean and the cut was
excellent, the light would be reflected through the top of the stone.

Realistically, we know that the stone will eventually get dirty.

Now here’s the question: is there any possible way to apply a mirror
backing to the stone? I’m thinking of the same process they use on
glass - they used to call it silvering, but I don’t know what process
they use now. I guess it’s what is used on rhinestones.

I can’t see that it would damage the stone in the long run, unless
heat is part of the process.

I’m sure that if this were a good idea it would be a common
application. But I still wonder if it would be feasible, and why not.

Just a thought. Thanks for any input.
I’m obviously not a gemologist.

Well…the moment you apply a reflective coating, the stone morphs
from a high quality gemstone to a treated or enhanced category. In
like you just changed a fancy intense pink sapphire into a foilback.
Whaaa? Somebody’s gonna pay you for that? Well, maybe they will.

I have to say my interpretation of this harkens back to a long ago
post about ‘good’ sapphires. What’s ‘good’, what’s ‘high quality’,
and who’s calling the difference? So if we’re talking about high
quality that infers high value, I would wonder about the economics
of it.

But if its just for giggles, yes the process for silvering glass
should work on a suitable gem candidate. I have never done it myself
but did for many years contract out a lot of mirror resilvering. I’m
told it involves applying an electroconductive coating and then
plating in silver and then covering with a dark protective stop.
Now, the mirror-iness of the finished product naturally relies on the
perfection of polish of the gemstone (or glass) surface before
plating. Its the rare cab that has its pavilion polished to that
standard. If its flat backed it most likely will have a slightly
frosty finish, if its flat backed and polished…I’ll venture that
its not really flat. If its got a belly to it there’s a reason for
that…weight, color, phenomena.

When you say fancy cut bottom, it suggests to me that maybe its
something like a moonface carving on the back?

In a similar challenge once, I was presented with an exceedingly
shallow, pale as can be yellow faceted saph about 12mm round (maybe 5
mm deep, yeah I said shallow!) to be set in a ring and still look
like something. The proverbial sow’s ear. With a picture window. I
made a gypsy ring in WG with an 18K gold socket that was shaped and
polished to give the effect I thing you’re going for. Trouble is
’cleaning’ right? I drilled one small hole below the seat where there
was still enough pavilion angle to hide it, visually from face up.
Steam thru there once a month and Bob’s your uncle. Now. is it
deceptive to alter the perception of color? Not in this case since
it was the customer’s ‘sentimental’ stone and they paid me to set it
to best advantage. Would a converted foilback gemmy stone be
deceptive? Really depends.

Have you considered dropping in a disc of fine silver the same size
as the bezel to (a) hide the unattractive backplate and (b) reflect
light back through the stone? I do this to make my cabs sparkle. The
fine silver won’t tarnish so it shouldn’t become a cleaning issue.

Hope this helps