Folium

n.	1.	A leaf, esp. a thin leaf or plate.
	2.	(Geom.) A curve of the third order, consisting of two infinite branches, which have a common asymptote. The curve has a double point, and a leaf-shaped loop; whence the name. Its equation is x3 + y3 = axy.

Noun

1.

folium - a thin layer or stratum of (especially metamorphic) rock

formation, geological formation