Here is what I think about these beautiful agate coasters, LOVE THEM!!!. No two agate stones are exactly alike and that’s the beauty of it. These semi precious stones are crystallized quartz and are so pretty on your kitchen or coffee table any day. These stones come in a wide range of colors which are brown, white, red, gray, pink, black, and yellow. I bought the pink pair and they’re beautiful not to mention a conversation piece.