Natural diamonds, cross polarized light (black diamond add)

Linden.g · Post by **Linden.g** » Fri May 08, 2020 8:48 am

I was very surprised by the intensity of the birefringence in these natural micro diamond crystals. The colours could only be seen with an extra lambda plate. All images were focus stacks using an Olympus S-plan Apo 10x except for the stereograms which were S-plan 4x.

houstontx · Post by **houstontx** » Fri May 08, 2020 9:14 am

awesome, what was the source of the diamonds? Were these for cutting/grinding? Love all of them, too bad about that inclusion on the first one

Linden.g · Post by **Linden.g** » Fri May 08, 2020 9:19 am

houstontx wrote:awesome, what was the source of the diamonds? Were these for cutting/grinding? Love all of them, too bad about that inclusion on the first one

Thanks so much, they were bought on ebay and were listed as GH White colour VS clarity. Use wasn't specified.

Pau · Post by **Pau** » Fri May 08, 2020 9:38 am

Excellent images, Linden

Diamond belongs to the cubic system and therefore if well crystallized doesn't present birefringence, it may be due to strain although I think that it would show with cross polars without needing lambda plate

info here...
https://www.researchgate.net/publicatio ... d_A_review

rjlittlefield · Post by **rjlittlefield** » Fri May 08, 2020 9:52 am

Lovely effect, lovely images!

I was thinking stress-induced birefringence also. (I assume that in this case "stress-" and "strain-" are two ways of saying the same thing?)

I notice especially that the defect in the first photo is surrounded by a whorl of color, and I'm thinking that's telling us something.

--Rik

Ken Ramos · Post by **Ken Ramos** » Fri May 08, 2020 9:52 am

Beautiful images

though they remind me of shocked quartz in a way or maybe a ZZ Top album cover.

Wonder if they were the result of an impact somewhere near where they were gathered? But if they were the result of an impact, near could be several hundred or thousands of miles away.

Linden.g · Post by **Linden.g** » Fri May 08, 2020 12:15 pm

Thank you for the appreciation, feedback and references. The birefringence is very weak under plan cross polarization. The crystals grow under extreme condition so perhaps its not too surprising they are highly internally stressed.

Scarodactyl · Post by **Scarodactyl** » Fri May 08, 2020 12:37 pm

rjlittlefield wrote:. (I assume that in this case "stress-" and "strain-" are two ways of saying the same thing?)

Stress is a force that the crystal experiences, strain is what happens in response to that force.

Olympusman · Post by **Olympusman** » Fri May 08, 2020 1:03 pm

Interesting.

Mike

Nathan Renfro · Post by **Nathan Renfro** » Fri May 08, 2020 11:23 pm

Nice photos . This strain birefringence is normal in diamonds. How big are these crystals? Diamonds are one of my favorite minerals to look at. In particular, their surfaces can be quite spectacular using epi DIC microscopy.

Charles Krebs · Post by **Charles Krebs** » Sat May 09, 2020 12:01 am

Really nice. Fascinating!

rjlittlefield · Post by **rjlittlefield** » Sat May 09, 2020 12:14 am

Scarodactyl wrote:
rjlittlefield wrote:. (I assume that in this case "stress-" and "strain-" are two ways of saying the same thing?)
Stress is a force that the crystal experiences, strain is what happens in response to that force.

Sorry, I should have been more explicit. Some sources refer to "strain-induced birefringence"; other sources refer to "stress-induced birefringence". Are those not the same effect, described by two different terms?

--Rik

Pau · Post by **Pau** » Sat May 09, 2020 1:04 am

At least in Geology stress is the cause and strain is the consequence of the applied stress, take a look at stress/strain curves. Stress is a directional pressure* while strain is deformation of the material, this is in the base of a whole scientific field: Tectonics.

Take a look at https://courses.lumenlearning.com/wmope ... nd-strain/ for example

*non directional pressure does not cause strain.

Pau · Post by **Pau** » Sat May 09, 2020 2:36 am

rjlittlefield wrote:...Some sources refer to "strain-induced birefringence"; other sources refer to "stress-induced birefringence". Are those not the same effect, described by two different terms?

Yes, basically they are the same, although the terms stress and strain are not equivalent: the direct cause is strain but the cause of strain is stress

WalterD · Post by **WalterD** » Sat May 09, 2020 3:27 am

Beautiful, beautiful colors! Thanks for sharing.

Regards,

Walter