One thing that is both neat and maddening about mosses is the fact that they can look so very different in different seasons or when moisture levels change.
This is rose moss, Rhodobryum roseum. I don’t think it is particularly rare, but I only know it from one spot–a rocky ledge over a creek in Cedar Bluffs State Preserve, Mahaska County, Iowa.
The kind of lumpy greenish mass in about the center of the photograph is it. The photograph at the very top was taken in late February.
This photograph was taken in April. The moss leaves have become darker and crinkled up a little. It has gone from a very showy, conspicuous plant to a plainer one.
I may not have seen it elsewhere because it is not as easy to see later in the season, and I have not visited a lot of woodlands in February when the moss is so showy.