Smithson’s three mirrors in a corner create a structure both lucid and elusive: as each mirror reflects the space around it, it multiplies the reflections in the other mirrors, creating an image with the symmetry of a crystal. Mirrors appear often in Smithson’s art, as do fragments of the natural world—here, there are pieces of coral piled in the angle where the mirrors meet. Smithson also combined mirrors with heaps of sand, gravel, and other rocks, matching nature’s brute rubble with its precise visual twin. (The delicacy of the lacy pink coral is unusual in his work.) The pairing of matter and reflection corresponds to another duality: on the one hand, unshaped shards of stone or reef; on the other, art, sculpture, and the indoor space of the gallery.