ˈbent ə nˌīt, -təˌnīt noun
( -s )
Etymology: Fort Benton, Montana + English -ite
1. : a soft porous moisture-absorbing rock composed essentially of clayey minerals often of volcanic origin
2. : any of numerous variously colored clay deposits containing montmorillonite as the essential mineral, characterized either by the ability to swell in water or by the ability to be slaked and to be activated by acid, and used chiefly in oil-well drilling muds, as fillers and plasticizers (as in paint and soap), as suspending agents (as in pharmaceutical preparations), and as carriers for agricultural chemicals
• ben·ton·it·ic |bent ə n|id.ik, -tə|ni- adjective