ˈsībə(r)d.ˌīt noun
( -s )
Etymology: French, from Henry Seybert died 1883 American mineralogist + French -ite
: a basic aluminosilicate Ca(Mg,Al) 3 (Al,Si) 4 (O,OH) 12 of the clintonite group consisting of calcium, magnesium, and aluminum, occurring in monoclinic crystals and foliated masses and having a reddish brown, copper red, or yellowish color and submetallic luster (hardness 4-5, specific gravity 3-3.1)