Question about Peacock Overtones.....

[mausketeer]

I've been looking at peacock Tahitians a lot lately (a lot of time on my hands) and I've realized something (please excuse me if this is obvious to the experts!). On the perfectly round pearls (and others but it's most obvious on round), peacock overtones ALWAYS flow in the same "direction" for lack of a better word: pink/red in the middle of the pearl, yellow, green, blue, purple. (rainbow). It's the same no matter WHICH way the pearl is turned, which of course indicates that the overtone colours are not actually ON the pearl itself, but is a result of the nacre (or is the concholin? Dave always talks about those two but it's a bit too technical) reflecting or refracting the light (I realized that the "middle" of the pearl would be the one that is the high spot and the light would hit that directly, and therefore would be red - the "thinnest" area of nacre for the light to get through - then would go down through the rainbow to the outside purple edges - thicker layer as it the light goes through almost sideways? Does this make sense?)

There was a question here somewhere.......not sure what it is...... I guess, why are peacock overtones so different than the other colours? Why does this stand out as such a..... distinct phenomenon? Any idea? Shouldn't ALL Tahitians that have overtones do the same thing?????

(again, if this is already a well known phenomenon, sorry! I was just so excited when I realized it I had to comment!)

- Jodie -

[jshepherd]

Hi Jodie -

What you are seeing is an optical phenomenon known as goniochromism, which we call iridescence when related to pearls. It causes the hue of the pearl to change colors depending upon the angle from which the pearl is viewed.

This comment might catch heat from Tahitian producers, but this optical illusion is often described incorrectly as orient. Orient comes from the thin-film interference and light diffraction caused when light passes through the nacre of a pearl. But a Tahitian pearl's nacre is opaque, so what you are seeing is iridescence and not orient. The iridescence, or lack thereof, is caused by the size of the aragonite platelets on the surface of the pearl.

[mausketeer]

Thanks Jeremy! Goniochromism. That's pretty cool! (now I'll have to see if other objects exhibit this - like, I guess opals do too, right?) Geez, and I'd just figured out the difference between lustre and overtones! lol

- Jodie -

[Caitlin]

Has anyone else ever read "The Splendor of Iridescence"? It's an old book with colored pencil drawings of iridescence. I love it. Tahitian pearls' iridescence is like that of hummingbirds'. The orient on most pearls is like fractured and fractalized iridescence. ? I am asking not telling.

[mausketeer]

Hey, three of my favorite things: butterfly wings, soap bubbles, gasoline (well, gasoline rainbows!).......

Found a cool Tumblr page with lots of awesome photos!
http://goniochromism.tumblr.com/

[Caitlin]

All iridescent! I remember the first time I saw oil slick as a youth, I loved the iridescence though I knew it spelled tragedy. I have a history of loving iridescence above any single color, except PURPLE! Or rather = to purple. Remember those purple iridescent fire beads? I think they have them on Fire Mountain. That type was the first strand of beads I ever bought to make jewelry. Back in 1966 from that San Francisco Institution, YONI BEADS! If you visit, read the history pages. I honor this man above many for being a genuine bead pioneer!

My original bead mentor and source of some of the world''s more beautiful and unusual beads. Mr Bee was original to the store as well, and is still there. MWaHH!!!!

[mausketeer]

Oh Caitlin - we are two of a kind I believe!!! Same here (that love of colours and swirling beautiful, bright, sparkly things started so young for me too!) I still get that excitement just like I'm a little kid when I see rainbows (REAL rainbows in the sky). Not quite like that guy on "You Tube" though. lol

Wow, to be in San Francisco in the 60's! I PINED for that when I was a teenager (born in 1965 - I always felt I was a decade too late!) I MUST come to one of the ruckus' and meet you to hear some of the stories you must have....... have a few glasses of wine!

- Jodie -

[Caitlin]

It's a date! My eldest, Kether, born in 1969, has attended previous ruckuses. Get the low down from her!