21 replies to this topic

[Adrian]

Some time ago there were a couple of posts about the discovery of Yooperlites in 2018: https://www.ultravio...__fromsearch__1

I have since done some more research, and finally managed to get my own (very small) specimen recently (from a UK dealer - the cost of sending a pebble from the US was exorbitant!)

To recap, Yooperlites are a newly discovered rock type found in Michigan's Upper Peninsula It has been called "yooperlites" after Yoopers the name residents of Michigan's Upper Peninsula give themselves ("U.P.-ers").
The rock has been identified by scientists in Michigan as "syenite rock that contains fluorescent sodalite", a mineral that had never before been identified in Michigan.

As can be seen the specimen photographed here was just 10mm across.

Technical details:
Camera Nikon D850, with 105mm micro Nikkor. UVF: 10 seconds @ f/16, 200ISO, light painted with Convoy S2+ UV torch.

Attached Images

• 
• 

[colinbm]

Good score Adrian
It looks like the Moon when it was still volcanic....;-)

[Stefano]

Yes, it looks almost incandescent, very cool.

[JMC]

Funky. It'd be interesting to see if its fluorescence is different with different UV wavelengths at some point.

[UlfW]

https://www.fluomin....DALITE&debut=10

[JMC]

UlfW, on 28 August 2020 - 14:22, said:

https://www.fluomin....TE&debut=10

Nice, thanks Ulf.

[Bill De Jager]

Nice find, Adrian. The fluorescing rock looks like a flaming meteor from a science fiction show.... that is, some movie/TV industry notion of what a meteor would look like.

The Upper Peninsula of Michigan, aside from being a beautiful place, has considerable mineral deposits stemming from events long ago in the Mesoproterozoic which ended about 1,000,000,000 years ago.The area is known for its deposits of native (naturally nearly pure) copper metal, among other diverse minerals.

[Andrea B.]

Very interesting!

And "Yoopers" made me laugh.

[JMC]

I've taken the plunge and bought a little sample of this (probably from the same place you got yours from Adrian - as you say postage from the US was not good). I plan on looking at it with fluorescence from 300 to 400nm illuminating it using 10nm bandpass filters on the light source to see if it makes any difference.

[Adrian]

Look forward to seeing the results!

[JMC]

My sample of Yooperlite arrived. Described as "Syenite with Sodalite. UV Reactive. Location: Lake Superior Mine, Michigan". My sample is about 2cm across.

Imaging done with an EOS 5DSR and Rayfact 105mm lens, with a 420nm long pass filter to block out the UV. UV Light source was a Hamamatsu LC8 200W lamp with a Xe lamp and collimator. Normal room lights used for visible light shot. White balance on Daylight for UV images, and Auto for visible light image. Captured as JPEG in camera and cropped and resized for sharing. No other modifications.

Visible light (f11, ISO1600, 1.3s)


Using a Baader U to filter the light (wide wavelength range of UV illumination, f11, ISO1600, 10s)


I also did a set of images with different UV bandpass filters on the light (10nm width from 310nm to 390nm). These were from Edmunds and Thorlabs. All are claimed to be OD4 blocking in the out of band regions. This was to try and see whether different wavelengths resulted in different fluorescence colours, and also different degrees of fluorescence.

However not all the filters let the same amount of light through, and the spectral distribution of the light source is not flat. To try and account for this, I measured the Irradiance spectra of the light, and then multiplied this by the transmission of the filters between 290nm and 420nm, the aim being to get some idea of 'total amount of light hitting the subject'. Then I used this to try and correct the exposure used for the visible light image. I have not idea whether this is correct, but it was the best I could come up with. Images below (these were all done at f4.5 as using the bandpass filters reduced the degree of fluorescence).



















My primary goal here was to see if the different illumination wavelengths resulted in a change in emission colour. Between 310nm and 390nm that does not appear to be the case. There are some examples online where using 254nm for illuminating rock samples results in a different coloured fluorescence to 365nm, but I do not have a filtered source that goes that low to test it.

Overall, a very pretty rock under UV.

Edited by JMC, 16 January 2021 - 10:21.

[Stefano]

Nice test Jonathan.

I do see a difference, it may be caused by the different exposures, but the lower wavelengths appear more orange. Maybe under UVC this rock would become reddish?

I am also curious to see another thing: usually strongly fluorescent substances appear darker than "usual" in reflected UV, since they re-emit a good amount of UV light as visible or infrared light instead of UV again. Thus common paper, highlighters and some laundry detergents appear dark or even black in UV. You can see this in this YouTube video by Veritasium at 3:30.

So, the point is: I expect the fluorescing areas of the rock to appear darker than the rest of the rock under reflected UV. Maybe you could try this if you want.

[Stefano]

I found a link similar to UlfW's: https://www.google.c...d=1604444094884

It appears that under SW UV sodalite is actually reddish-pink.

[colinbm]

Nice photos Jonathan, it sure is a bright fluorescence.

[JMC]

Thanks all. Yes perhaps if I look at it, the 310nm and 320nm images have a bit more of a pink tinge to them.

Stefano, I'll try and get some UV reflection images done, to compare with visible and fluorescence. Probably just with the 365nm torch though instead of the Xe lamp (should still show the effect).

[Stefano]

JMC, on 04 November 2020 - 12:20, said:

Stefano, I'll try and get some UV reflection images done, to compare with visible and fluorescence. Probably just with the 365nm torch though instead of the Xe lamp (should still show the effect).

Yes, a 365 nm torch will work fine.

[dabateman]

Interesting. Your 330nm image and your 380nm images are significantly different. More rock is glowing in the higher illumination wavelengths. So might be some differences if you look at the green, blue red channels.
You could but them in the current USA colors with 0.2% green, 50% blue and 49% red. I should see what images look like with those distributions.

[JMC]

Quick experiment using a multispectral converted EOS 5DSR with Rayfact 105mm lens. ISO 1600 and f11. Images captured as RAW and jpeg in camera. Spectralon diffuse reflectance standard imaged at same time.

Visible light image - LED room lights, Chinese BG39 (2.5mm) filter and 420nm long pass filter, white balanced in Darktable.
UV induced fluorescence - 365nm Nemo torch, additional filter on torch (Baader U), Daylight whitebalance
UV reflectance - 365nm Nemo torch, Baader U filter on lens, whitebalanced in Darktable.

Images cropped and resized for sharing. No other manipulation.






For me, there is no strong correlation between 'dark in UV reflection' and 'strong UV induced fluorescence'. Some areas which fluoresce under UV look dark in UV reflectance, some look light.

[Stefano]

Thanks Jonathan. Yes, it doesn't appear there is a strong correlation. The rock actually looks more uniform in UV.

BTW, the UVIVF image is so cool. It looks so bright.

[JMC]

No problem Stefano. Yes the Yooperlite fluorescence is very strong. Certainly worth getting a sample if you can. And that Nemo torch is incredibly bright, excellent for fluorescence work - it'd be really good for light painting.

I may try putting it on my reflection microscope and try and get some high magnification images of fluorescence.