Definition of plumasite in US English:

plumasite

noun

Geology
  • A plutonic rock, typically coarse-grained and found especially in dykes, consisting chiefly of corundum grains in an oligoclase matrix.

Origin

Early 20th century. From the name of Plumas County, California, where it was first found + -ite.

Pronunciation

plumasite

/ˈpluːməsʌɪt/