Wilson's Dictionary of Bible Types
Exodus 28:17 (c) The first stone on the breastplate of the high priest was the ruby. It was red in color to represent the precious Blood of CHRIST. It bore the name of Reuben which has two meanings: "one who hears acceptably," and "one who is the son." All of this signifies that the one who hears the Gospel, accepts the Lord JESUS, and takes advantage of the shed Blood of CHRIST at Calvary, becomes as a precious stone for GOD and will one day be with the Lord when He makes up His jewels. (The word "sardius" means "ruby").
Job 28:18 (a) Here the ruby, which has greater value than the diamond, is contrasted with the great value of wisdom. Wisdom is the most precious of all the gifts of GOD to men of earth. (See also Proverbs 3:15).
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Watson, Walter. Entry for 'Ruby (Stone)'. Wilson's Dictoinary of Bible Types. https://www.studylight.org/dictionaries/eng/wdt/r/ruby-stone.html. 1957.