O afflicted one, storm-tossed and not comforted, behold, I will set your stones in antimony, and lay your foundations with sapphires. I will make your pinnacles of agate, your gates of carbuncles, and all your wall of precious stones. (vs. 11&12)Mosaics when done right, can be beautiful works of art. Perhaps I could get away with saying it's a rawer form of creating a stain glass piece. Mosaics heavily depend upon their lighting though. They can only sparkle the best when light can filter through them, casting vibrant, colorful shapes and shadows. Often the start with the artist sanding down rough, sharp shards of broken glass. The pieces are carefully placed in a specific design, then solderer together to create the final piece. God is doing this very thing here. The image Isaiah is displaying here is one in which God promises His people that He will restore them to be a glistening city on a hill.
God's children are likened to a sapphires, set against antimony (a dark, shiny gray/sliver mineral), creating this mosaic fortress to showcase His light and glory to other nations. Sapphires are the second strongest precious gem found in weathered stream beads or mountain valleys, in a variety of different colors. Like all precious jewels, once harvested, they have to go through an extensive refinement process. They have to be purged of their impurities in order to become clear and glistening. A couple verses later we see God likening Himself as a (black)smith... as our refining fire. See, before sapphires become wedding ring worthy, they start off as these rough, milky rocks... nothing particularly pretty, but after that refining process they are valuable and have worth. So it is for you and I without Christ... without Him we are nothing. It's through His death and resurrection... His covenant, that we are now (and continually) refined into beautiful gems. Not because we deserved it, but because of His grace, mercy, and love towards us. The beauty of any gem can be only admired in His light. You and I are to be those gems that encrust His city on a hill, filtering His light to others:
You are the light of the world. A city set on a hill cannot be hidden... let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven. ~Matthew 5:14-16, emphasis mine
The deep foundations of the work of grace are as sapphires for preciousness, no human mind is able to measure their glory. We build upon the covenant of grace, which is firmer than adamant, and as enduring as jewels upon which age spends itself in vain. Sapphire foundations are eternal, and the covenant abides throughout the lifetime of the Almighty. Another foundation is the person of the Lord Jesus, which is clear and spotless, everlasting and beautiful as the sapphire; blending in one the deep blue of earth's ever rolling ocean and the azure of its all embracing sky. Once might our Lord have been likened to the ruby as he stood covered with his own blood, but now we see him radiant with the soft blue of love, love abounding, deep, eternal. Our eternal hopes are built upon the justice and the faithfulness of God, which are clear and cloudless as the sapphire. ~Charles H. Spurgeon