silver-gold-antimony? whats antimony?

Isaiah 54
11 “O afflicted city, lashed by storms and not comforted,
I will build you with stones of turquoise, [a]
your foundations with sapphires. [b]
12 I will make your battlements of rubies,
your gates of sparkling jewels,
and all your walls of precious stones.
You know, I’ve read this passage a million times over the years.  I’m am not really [...]