Peridotite - Rock Thin Section

CaptainPleco · Post by **CaptainPleco** » Mon May 22, 2017 6:17 am

This is my first posting on this Group so hopefully it will work OK!

I was inspired by the British Geological Society (BGS) Project to digitise their archive collection of 190,000+ rock thin sections.
Using my Canon 450D DSLR camera, fitted with the standard 18-55mm lens and a 12mm extension tube I captured the whole thin section.
Despite not having a macro lens the image is reasonably sharp towards the edges.
The slide was ‘sandwiched’ between polarising filters and backlit using a Kaiser LED lightbox.
The camera was mounted vertically above the slide and fine focussing was achieved using a laboratory scissor jack.
The peridotite slide contains olivine, twinned and normal zoned plagioclase feldspar, augite and chlorite.

ChrisR · Post by **ChrisR** » Mon May 22, 2017 10:37 am

Welcome to the forum!
Nice slide, I think. I have a few thin sections but getting off the ground with identifying them isn't easy!

Do you find the image is blurred at the edges because the field isn't flat? If that's the case, a short "focus stack" of a few images would be likely to make a big improvement.

What polarisers are you using?

CaptainPleco · Post by **CaptainPleco** » Mon May 22, 2017 11:37 am

Hi Chris.

Thanks for the advice on the field flattening technique.

I purchased a sheet of polarising film (20x25 cm) from greenweld.co.uk, Stock No. OPF0041 as it had a good specification. The polarising film was cut to size and sandwiched between the two glass cover slips from Gepe 3mm Slide Mounts (6 x 6 cm). The rock thin section was held in place between two slide mounts in crossed polar configuration. Hope that makes sense?

This is a very good website for purchasing and identifying rock thin section minerals.
http://www.geosecslides.co.uk/minerals/MIAindex0.4.html

Pau · Post by **Pau** » Mon May 22, 2017 12:41 pm

CaptainPleco,
Nice low cost setup.

I think I recognize this slide...I have one like it from Rob (Geosec)

Chris, I'm not bad in Petrography, I could help you in identification or recommend some books

CaptainPleco · Post by **CaptainPleco** » Wed May 24, 2017 4:23 am

Pau.
Thank you. The idea was to get a full size image of the slide which would not be obtainable using a microscope.

Chris R.
I can recommend 'A Colour Atlas of Rocks and Minerals in Thin Section' by W. S. MacKensie and A. E. Adams. I believe its out of print now but used copies are available from Amazon.