Plants in hoary, dense tufts, dark green to dark brown. Stems 0.5--2 cm. Stem leaves oblong-ovate to oblong lanceolate, 1.5--3 × 0.4--0.6 mm, both margins plane, intermarginal bands absent, awn 0.3--2 mm, decurrent, acute, costa broad proximally; distal laminal cells 2-stratose, quadrate, thick-walled; medial laminal cells rounded quadrate, straight, thick-walled; basal juxtacostal laminal cells elongate, straight, thick lateral walls, green; basal marginal laminal cells oblate to quadrate, straight, thick transverse and thin lateral walls, green, not hyaline. Perichaetial leaves not enlarged. Seta straight, 1.5--3 mm. Capsule occasionally present, exserted, brown, oblong-ovoid to cylindric, exothecial cells quadrate, thick-walled, stomates present, annulus of 2--3 rows, rectangular, thick-walled, operculum short rostrate, peristome irregularly perforate distally, irregularly split. Calyptra mitrate.

Humid to dry, exposed, acidic, sandstone and granite and basalt, open plains to montane, rarely alpine; 240--2800 m; B.C.; Ala., Ariz., Ark., Calif., Colo., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., Md., Mass., Minn., Mo., Mont., Nebr., Nev., N.J., N.Mex., N.Y., N.C., Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., Wyo.; Mexico; South America; Eurasia; Africa; Indian Ocean Islands; Australia.

Grimmia laevigata is widespread and relatively common on the southern Great Plains, into the Ozarks and along the Appalachians from northeastern Alabama to the New England states. There is also an extensive outlier in southern Minnesota and adjacent states. In western North America, it is abundant in California and the Pacific Northwest region into south central British Columbia. Although occurring in the Rocky Mountain region it is not common, being found mostly in lower elevation sites and along the east slopes. With the exception of a few disjunct sites in southern Georgia and Florida, it is unknown from the coastal plains of the American southeast. This is probably related to the extensive cover of calcareous Cretaceous and more recent bedrock. The northern limit of G. laevigata suggests a distribution influenced by the winter position of the Arctic airmass. Although known from high elevations, G. laevigata is most often found below treeline on granite and acidic sandstones. It is an early successional invader of granitic rocks in the piedmont of the American southeast (H. J. Oosting and L. E. Anderson, 1937, 1939 and C. Keever et. al 1951). Classic specimens of Grimmia laevigata are recognized by their broad leaves with almost no shoulder separating the proximal and distal lamina, and by their robust, broadly attached and long-decurrent awns. However, G. laevigata is quite variable with respect to leaf shape and awn attachment with some specimens having bases approaching ovate and then often with rather narrowly attached awns. These specimens may be assigned to G. laevigata by the a wide costa and oblate to quadrate basal marginal cells.