Rock tripe is a lichen

Lichen

Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...

 of the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Umbilicaria that grows on rocks. It can be found throughout northern parts of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 such as New England

New England

New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...

 and the Rocky Mountains

Rocky Mountains

The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...

. It is edible when properly prepared and has been used as a food source in extreme cases when other food sources were unavailable, such as by early American northern explorers.

The closely related Umbilicaria esculenta

Umbilicaria esculenta

Umbilicaria esculenta is a lichen of the genus Umbilicaria that grows on rocks. It can be found in East Asia including in China, Japan, and Korea . It is edible when properly prepared and has been used as a food source and medicine...

 is commonly used as a food in Asian cuisine

Asian cuisine

Asian cuisine styles can be broken down into several tiny regional styles that have roots in the peoples and cultures of those regions. The major types can be roughly defined as East Asian with its origins in Imperial China and now encompassing modern Japan and the Korean peninsula; Southeast Asian...

 and a restorative medicine in traditional Chinese medicine

Traditional Chinese medicine

Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...

.