From an unused root (probably identical with that of shabah through the idea of subdivision into flashes or streamers (compare shabiyb) meaning to flame; a gem (from its sparkle), probably the agate -- agate.
see HEBREW shabiyb
H7618. shebo
שְׁבוֺ noun [feminine] a precious stone (relation to above √ dubious; = Assyrian šubû ᵑ9 ᵐ5 agate); — Exodus 28:19=39:12 (+אַחְלָ֑מָה לֶשֶׁם,).