Your choice for closest parallel in nature to a hologram?

Holography related topics.
Joe Farina
Posts: 711
Joined: Wed Jan 07, 2015 2:10 pm

Your choice for closest parallel in nature to a hologram?

Post by Joe Farina » Tue Dec 22, 2020 10:02 am

I was wondering what you might pick. Having a new interest in minerals and gems, I was surprised to see some effects which, I believe, are the same thing as a hologram.

With reflection holograms in mind, I would say that holograms are repetitive regular changes in refractive index, where the distances for the changes are around the wavelengths of visible light. Another requirement (for a reflection hologram) would be that both index-changing regions are transparent. (Maybe I'm missing other requirements.)

I have a couple samples of labradorite (one of which is called spectrolite), and have seen some opals in a gem store. All the color effects (and the appearance of the reflected wavefronts of light) seem identical to a reflection hologram. The Australian opals are amazing, the intensity of colors seems to surpass any hologram I've seen.
The attachment spectrolite.jpg is no longer available
spectrolite.jpg
spectrolite.jpg (22.98 KiB) Viewed 360 times

Din
Posts: 259
Joined: Thu Mar 12, 2015 4:47 pm

Re: Your choice for closest parallel in nature to a hologram?

Post by Din » Tue Dec 22, 2020 10:17 am

You're right about labradorite and opals. With opals, air gets into the stones during formation creating a random set of bubbles. The spacing of these bubbles, being random, creates the flashes of colour that change as you move them around. Wit labradorite, there's only one, sometimes two, planes, so thhere are no flashes, but there is Bragg selectivity - just as in a volume hologram. We've been collecting gemstones for about 15 years now, and wife, Joy, is particularly fond of opals because of the connection with holography. Here's an illustration from a book about opals (Notice, they reference C V Raman, the one who discovered the Raman effect):
opal.jpg
opal.jpg (72.3 KiB) Viewed 354 times

Joe Farina
Posts: 711
Joined: Wed Jan 07, 2015 2:10 pm

Re: Your choice for closest parallel in nature to a hologram?

Post by Joe Farina » Tue Dec 22, 2020 10:24 am

Thank you Din, this is amazing.

Din
Posts: 259
Joined: Thu Mar 12, 2015 4:47 pm

Re: Your choice for closest parallel in nature to a hologram?

Post by Din » Tue Dec 22, 2020 10:26 am

However, one thing you may not see very often, because it's incredibly rare, is an opalised petrified wood. When the wood, a tree for example, lies on the ground long enough, minerals enter the tree, while the wood rots. Eventually, the minerals take on the form of the wood creating petrified wood. There's a whole forest of petrified wood outside San Jose called the petrified forest. However, during the formation of the petrified wood, rarely, bubbles begin to form of just the right spacing. The petrified wood is now also an opal.
Attachments
pet-opal.jpg
pet-opal.jpg (195.63 KiB) Viewed 352 times

Joe Farina
Posts: 711
Joined: Wed Jan 07, 2015 2:10 pm

Re: Your choice for closest parallel in nature to a hologram?

Post by Joe Farina » Tue Dec 22, 2020 10:30 am

I didn't know about opalised petrified wood -- I see those those flashes of color in the photo, thanks for posting.

dannybee
Posts: 609
Joined: Tue Jan 06, 2015 10:29 pm
Location: visalia
Contact:

Re: Your choice for closest parallel in nature to a hologram?

Post by dannybee » Tue Jan 19, 2021 9:50 pm

Opals Of The World (1).jpg
As you do macro photography the world become a world of rainbow's of light, and very trasparent, with plants and insects, a wonderful inter play of light
Opals Of The World (1).jpg (182.78 KiB) Viewed 267 times

dannybee
Posts: 609
Joined: Tue Jan 06, 2015 10:29 pm
Location: visalia
Contact:

Re: Your choice for closest parallel in nature to a hologram?

Post by dannybee » Tue Jan 19, 2021 9:52 pm

Very much like the inter play of light in opals

Post Reply