Cheim & Read, of New York, is offering up this 1959 Joan Mitchell, which has never before been seen in public. The (The collector consigning it got it directly from the artist, per the gallery. By the time she made it, Mitchell had five New York solo shows under her belt, all at the Stable gallery.) It’s modest in size—46 inches by 35 inches—but it packs a wallop, with tough, broad, quick slashes of green-gray dashed with purple, orange, and teal. A little slice of heaven.