And clear as diamonds, when facing an excellent example (as your necklace). Still...
When forced to discriminate between genuine and fake, we realize that although many fakes mimic their genuine models so well they even the experts are deceived, the genuine pieces do not look like fakes at all.
Concerning products of activities officially aknowledged as artistry sometimes just plain bad taste (good taste does not exist, but bad taste does) is used as a substitute for real creativity, and commercially uphold so-called artists are listed as geniuses by lobbies. Then trust in our own capacity of discrimination may betray us, and we may consequently comply: "Such a degree of celebrated ugliness must be great art".
If I had to answer what good taste essentially is in my opinion, I would create the category out of thin air and say: restraint.