en_tn/rev/21/11.md

Jerusalem

This refers to the "Jerusalem, coming down out of heaven" that he described in the previous verse and not to the physical Jerusalem.

like a very precious jewel, like a stone of crystal-clear jasper

These two phrases mean basically the same thing. The second emphasizes the brilliance of Jerusalem by naming a specific jewel. (See: rc://en/ta/man/translate/figs-parallelism)

crystal-clear

"extremely clear"

jasper

This is a valuable stone. Jasper may have been clear like glass or crystal. See how you translated this in Revelation 4:3. (See: rc://en/ta/man/translate/translate-unknown)