What is mirror made of?

Glass, silver paint (or foil) and black paint. The silver paint or foil reflects the light that hits it, the black paint prevents light from behind washing out the image and helps protect the reflective surface from damage. The glass also helps protect the reflective surface as well as focus the reflective image.

AnswerThe elements that make up mirrors are silycon, oxygen, and silver.

Modern mirrors are made by vacuum deposition of aluminum onto a smooth base, then covering with glass. The glass makes for a smoother surface and also protects the aluminum from damage. Fundamentally, the plate is placed in a chamber which is then evacuate. Aluminum is vaporized, and condenses on the surface of the plate.

Also, aluminum can be vacuum deposited to the glass itself. It is often given a black backing to improve opacity and reflectivity. At one time Mercury was used, but no longer due to health an environmental issues.