Micranthes rhomboidea is found over a wide range of elevations but is most common in the high mountains, in the tundra zone above the treeline. Leaves grow only at the base; they are thick and fleshy, with coarsely toothed edges. The upper surfaces of the leaves are smooth and hairless, while the lower surfaces have a sparse covering of brownish, cobweb-like hairs. Leaves are attached by flattened stalks about one inch long. Leaves taper gradually at the base, giving them an approximate diamond-shape.
The inflorescence is a compact, slightly elongated cluster containing between 10 and 40 flowers, at the upper end of a stout, reddish stem, densely covered with yellowish, glandular, head-shaped hairs. Flowers have five ascending, green sepals below and between five white, clawed, oblong petals. Petals are a little longer than the sepals. The five stamens have green filaments and yellow anthers.