Sapphire crystal glasses

Jewelry Discussion
1

Hello

I am interested to know they make these Sapphire crystals for
watches? Synthetic sapphire always shows some birthmarks. but with
these crystals (glasses)I did not see any any such under 10 X please
help me clearing this.

Thanks in advance
Tomy Joseph

2

How do they make them so perfect? Very carefully. They pull the
crystals more slowly, anneal more carefully, etc.

Sapphire watch crystals are made to higher standards than ordinary
synthetic sapphire. If you’re talking about sapphire to be used to
make silicon on sapphire (SOS) semiconductors they’re made even more
carefully – and the price is a whole lot higher than watch crystals.

3 
synthetic sapphire always shows some birthmarks. but with these
crystals (glasses)I did not see any any such under 10 X please help
me clearing this.

If you referring to strie, watch crystal does not have enough of the
thickness to make it obvious. In any even, strie should be observed
at low magnification and the right kind of lighting.

Leonid Surpin

4 
I am interested to know they make these Sapphire crystals for
watches? Synthetic sapphire always shows some birthmarks. but with
these crystals (glasses)I did not see any any such under 10 X
please help me clearing this.

Flame fusion synthetic blue sapphire or other colors often show color
banding. But modern material is well enough controlled that you no
longer are likely to see things like air bubbles. And colorless
material won’t show color banding. And flame fusion is the oldest
type of synthetic. Most likely, the methods used to produce watch
crystals, which generally are quite a bit larger than flame fusion
boules, will be the more modern “pulling” methods. These methods are
quite capable of producing virtually flawless material in much larger
pieces than the old flame fusion methods. Think of the methods used
to produce things like the very large diameter silicon rods that get
cut into wafers for semiconductor electronics, or the rods of
synthetic ruby or YAG or other materials used for laser rods. All
these need to be virtually flawless and pure. The synthetic sapphire
material for watch crystals is similar. In short, your assumption
that synthetic sapphire material always shows birthmarks that you
could find with a 10x loupe simply is no longer true for this type
of material. An advanced lab can of course identify it as synthetic,
but most such material no longer shows visible defects, and if there
were any such, those pieces would not make it into finished crystals.

Peter

5 
All these need to be virtually flawless and pure.

There’s a rather fascinating book called, “Gems Made by Man”. that I
have put away somewhere. It’s not so old but not so new, so it could
be the technology is out of date at this point. He talks about the
flame fusion methods, both dripping and pulling. That gives either
boules or rods. Then, when high crystalline purity is need, as for
laser rods, they get the rod and remelt it with plasma, starting at
one end and going to the other. The rod recrystallizes where the
plasma heats it, and the rod stays the same shape. Not something most
of us have in the back bedroom.

6

It’s called “zone refining” in the semiconductor industry. The melt
zone also sweeps out the impurities in the sapphire or silicon.

RC