It typically occurs as blue-green to olive green fibrous to lamellar masses.

It is translucent and glassy with a Mohs hardness of 5.5 and a specific gravity of 3.2.

Pumpellyite occurs as amygdaloidal and fracture fillings in basaltic and gabbroic rocks in metamorphic terranes.

It is an indicator mineral of the prehnite-pumpellyite metamorphic facies.

It was first described in 1925 for occurrences in the Calumet mine, Houghton Co., Keweenaw Peninisula, Michigan, and named for United States geologist Raphael Pumpelly (1837–1923).