Plants in small dense cushions or turfs, yellow-green to dark olive, hoary. Stems 5--20 mm, sparsely branched. Stem leaves crowded, ovate to obovate, imbricate to appressed-julaceous distally, somewhat spreading to squarrose-recurved proximally, 0.6--1.2 mm excluding awn, apex acute to acuminate, lamina 1-stratose to rarely 2-stratose in bands, awn length highly variable, 0.3--1.4 mm, hyaline; costa in transverse-section distinctly keeled; mid-leaf cells isodiametric to short-oval, (5--)8--12(--20) µm, distal cells somewhat longer, proximal cells rectangular, 15--40 × 10--20 µm, often appearing lax. Sexual condition autoicous; perichaetial leaves with lamina to 1.5 mm, awn 1--1.7 mm. Seta 0.4--0.6 mm. Capsule yellow-brown turning red-brown with age, ovoid to subglobose, 0.8--1 mm; operculum short-rostrate, 0.5--0.6 mm.

Capsules mature spring--summer depending on elevation. Widespread and locally common on dry sandstone or limestone rock, open arid to semi-arid shrub, woodland communities, grasslands, rarely on compacted sandy soil; 200--2100 m; Alta., Ariz., Calif., Colo., Iowa, Kans., Minn., Mont., Nebr., Nev., N.Mex., Okla., S.Dak., Tex., Utah, Wis.

Jaffueliobryum rauii is a common species in drier parts of the U.S.A., especially on the Great Plains and southwest on the Colorado Plateau, extending to the Mohave Desert of California. This species appears to be disjunct to southern Alberta, but the distribution is likely continuous as the band of calcareous bedrock that on which Jaffueliobryum occurs runs along the Rocky Mountain Front Range from Alberta well into Montana. Sites in the Driftless area of Iowa, Minnesota, and Wisconsin may be truly disjunct. However, more collecting is likely to fill in the gaps in its range in the northern Great Plains and clarify its status in the Great Basin. Jaffueliobryum wrightii is very closely related, and the two species have been treated as one for much of their taxonomic history. In addition to traits used in the key, there are a variety of other partially overlapping characters that separate the two, including leaf width at widest point, lamina length, costal width, lamina cell length and angle between the margin at the leaf widest point and the tip of the awn, and capsule and operculum length.