No clear is not a color--it is a property-- just like translucence-- I loved it when i discovered some "stones" are translucent! Some like most marbles are "opaque" but some like agate-- are translucent. there is a lovely church in Rome, that has agate not stained glass windows--
and i think a polarizing effect can be found in some natural materials, too. by that i mean they will allow certain frequencies of light to pass, but will block others-- and the effect depends on the position of the materal relative to the light source...
"florecent" is not just a "light type" but a property too, some materials absorb or reflect UV (ultra violet) light-- and while we can't see the UV light, we can see the change in color or reflectiveness of the material-- so UV lights are used to create "psychedelic" colors. And many clothing detergents use UV dyes to make clothes look "brigher" --remember the last time you went to a disco-- and your shirt looked dull-- the plastic buttons glowed? the UV dyes don't work well on man made fabrics-- but do on many plastics.. so your polyester shirt didn't glow- but the plastic "pearl" buttons did!
I have a black (UV) light for my rock collections. its always fun when someone gets close to see what else will glow in light. some diamonds (but not all) will as will many real gem stones.
