but siloxane react with alcohol can to form silanol.

At room temperature?

Indeed there is no reaction between amethyst and ethanol

With out this, then science can not justify the myth ;)

It also means:

Sometimes, the ancestor's behavior can be answered scientifically, for example, they insert Amethyst gemstones into glass to prevent drunkenness, this can make sense, because the nature of silica can be used as absorber with siloxane cluster (group), so the siloxane can absorb the toxic gas, moisture, etc.

That you can't conclude this. Because the people of yesteryear were not correct, amethyst did not prevent drunkenness.