I find myself grateful for this often. In doing this painting, I researched how mirror is made because I've always wanted to know.
Wikipedia says "The earliest manufactured mirrors were pieces of polished stone such as obsidian, a naturally occurring volcanic glass. Examples of obsidian mirrors found in Anatolia (modern-day Turkey) have been dated to around 6000 BC."
Without this invention, cameras would not have existed! How much art would not have been possible without a mirror...