Gemstones like precious opal are beautiful to look at and deceivingly complex. As you look at such gems from different angles ...

Is your green my green? Probably not. What appears as pure green to me is likely to look a bit yellowish or bluish to you. This is because visual systems vary from person to person. Moreover, an ...

A while back, I wrote about why there are no green stars in the sky (you should read that post first; some of the concepts below are explained there). But that’s not to say there are no green objects ...