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Identity Helpmineralized porphyry

28th Jul 2015 22:13 UTCOlivier Langelier

Hi,

This is a piece of porphyry that I found in the Grenville province. I sliced and polished

it and revealed numerous small vugs which I then explored with my digital microscope.

All I know is the phenocryst in the rock look like feldspar, and I see spinel in the vugs,

but there's also a yellow metallic substance that could be twinned with the spinel in

some cases.

Any observations about any part of the rock are welcome!

29th Jul 2015 14:50 UTCReiner Mielke Expert

I can't get any sense of what the structure or relationship of the yellow stuff is to anything else from your photos. Just looks like a yellow coating of some type. Doesn't look metallic from your photos unless you are thinking of gold which would not be found in such an environment. I would get EDS done on it before making any decisions as to what it might be since there are many possibilities such as a rinkite group mineral. On the other hand it could just be geothite?

29th Jul 2015 22:40 UTCRalph S Bottrill 🌟 Manager

Spinel would be unlikely, maybe magnetite, way too blurry to see anything. The yellow could be an iron-stained clay?

19th Aug 2015 18:49 UTCGregg Little 🌟

Olivier;

There is a trick field geologists use that can distinguish gold from the host of other suspects like iron staining and pyrite. Put a drop of water on the suspect mineral and if the appearance becomes dull when viewed from all or most angles, then it is not likely gold. Gold will retain its brilliance through the water coating when viewed from any angle. I hope this works for you.

20th Aug 2015 04:12 UTCPaul Brandes 🌟 Manager

Doesn't appear to be gold as I'm not seeing a metallic luster.

You'll likely have to do some analytical testing like EDS or possibly XRD if you can get enough material.