Some puzzling crystals

Images made through a microscope. All subject types.

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Cactusdave
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Some puzzling crystals

Post by Cactusdave »

This is a quiz I don't know the answer to myself. I bought this interesting slide on eBay. It has some pretty red crystals and a rather enigmatic label. First a rather bad macro shot of the subject and one of the label.

Image

Image

It doesn't look like a mineral, but 'porphyrins' are a class of complex organic molecules of biological origin, only fairly recently fully understood https://en.wikipedia.org/wiki/Porphyrin . They are not very stable and seem somehow unlikely to be the true subject of this rather old looking microscope slide.

Looking under the microscope reveals rather beautiful fern shaped bright red crystals. There are also some smaller colourless cubic crystals resembling common salt NaCl.

Image

Leitz X10 plan fluorite objective, diffused incident illumination.

Allowing the tiniest trickle of transmitted light simultaneously, shows this:

Image

Leitz X6.3 planfluorite objective, incident light plus highly attenuated transmitted light (ND filters).

As can be seen from the macro shot the crystals are embedded in some sort of yellowish coloured matrix.

Image

Leitz X10 plan fluorite objective, incident light plus highly attenuated transmitted light (ND filters).

Anyone any idea what these crystals might truly be?
Leitz Ortholux 1, Zeiss standard, Nikon Diaphot inverted, Canon photographic gear

Pau
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Post by Pau »

Really no idea, just some speculative clues:
- porphyrine as synonym of porphyrin (the nitrogenated cycle present in chlorophyll and proteins like hemoglobin) doesn't seem to fit here

maybe something more exotic
https://en.oxforddictionaries.com/definition/porphyrine

The slide seems a petrological thin section, if so it may refer to porphyr, an igneous rock with big crystals in a matrix of small crystals or glass. The term porphyr was used in the past (and still is in ambits outside Petrology like Archeology) in a much less strict sense, so maybe it could fit.

https://books.google.es/books?id=yLc7AQ ... gy&f=false

Take a look under cross pol like petrologists always do and post your results
Pau

JL
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Location: Houston, Tx

Post by JL »

I can think of a couple of possibilities.

1) A thin section of the mineral Abelsonite, it is described as a "nickel porphyrin". https://www.mindat.org/min-1.html

2) A sample related to deposits of decaying organic matter and probably related to the mineral struvite. This mineral has been found in animal farms sumps, in Spain it is known as purines pits. http://espiadellabo.com/2016/09/noticia ... e-la-vida/

Cactusdave
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Joined: Tue Jun 09, 2009 12:40 pm
Location: Bromley, Kent, UK

Post by Cactusdave »

I suppose Pau's obscure Australian tree alkaloid is a definite possibility. That's exactly the kind of thing the Victorian slide makers liked, but it's supposed to be colourless unless reacted with strong acids. Images of sections of porphyry minerals from the web don't look anything like my specimen. Abelsonite was only discovered in 1975 and this slide surely well pre-dates that. The matrix the crystals are in looks more like fixed gelatine or Collodion than a mineralogical matrix to me.
Leitz Ortholux 1, Zeiss standard, Nikon Diaphot inverted, Canon photographic gear

gpmatthews
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Post by gpmatthews »

Graham

Though we lean upon the same balustrade, the colours of the mountain are different.

Cactusdave
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Post by Cactusdave »

Graham - I don't think it's Porphyry.
Images of sections of porphyry minerals from the web don't look anything like my specimen.
IMHO it looks more like chemical crystals embossed in a matrix rather than a petrological section. The use of the word 'section' on the label may be misleading. Possibly it may mean 'part of' or 'piece of' rather than a thin section as we are used to thinking of it.
David
Leitz Ortholux 1, Zeiss standard, Nikon Diaphot inverted, Canon photographic gear

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