This is how much gold was used to paint or coat 18 mirrors of James Webb telescope (Webb's primary mirror is 6.5 meters (21 feet 4 inches) across). ~48 grams of gold. Thickness of gold coating = 100 x 10-9 meters (1000 angstroms).

https://bit.ly/35b2mqW via /r/spaceporn https://bit.ly/3s3iu79