Complex sentence: Mont Saint-Grégoire (height:) is a hill in the Montérégie region of southern Quebec; it is composed of essexite and syenite, strongly contrasting with the surrounding sedimentary rocks.
Split into simpler sentences: Mont Saint-Grégoire (height:) is a hill in the Montérégie region of southern Quebec. The mountain is composed of essexite and syenite, strongly contrasting with the surrounding sedimentary rocks.