The following image is of polished sample of mineral-rich rock. There are two major portions we can see that is ore minerals and rest the grayish material is gangue. The photo was taken with an ore microscope.
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2$\begingroup$ Interesting question and cool image! I've made a slight edit to your question. Recently "rock identification" questions have been decided to be off-topic, so to avoid any close votes I modified it to be "What minerals are likely to be found..." and "What can we deduce." $\endgroup$– uhohFeb 24, 2020 at 12:14
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2$\begingroup$ This has been discused and thin section questions are encouraged, aswell as fossils. $\endgroup$– user18590Feb 24, 2020 at 13:18
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$\begingroup$ Can you provide the link where this is discussed?@Universal_learner $\endgroup$– Lakhwinder SidhuFeb 25, 2020 at 5:18
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2$\begingroup$ earthscience.meta.stackexchange.com/q/1775/18590 $\endgroup$– user18590Feb 25, 2020 at 8:35
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1$\begingroup$ @Universal_learner I hadn't seen that, thanks! $\endgroup$– uhohFeb 25, 2020 at 10:52
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1 Answer
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Sulfide ore petrography is reflected light is even harder than transmitted light. Unlike transmitted light, colour is actually a very important characteristic feature. But the perception of colour can vary between different light sources, quality and time since polish, microscope lens, and cameras. Therefore, from an image like that it is extremely challenging to tell what the minerals are.
In my opinion you have two of either chalcopyrite, pyrite, pentlandite, pyrrhotite. It is very hard to tell. My guess would be pyrite (the bright one) and chalcopyrite/pentlandite (the golden one).
In cases like this, as a way to move forward, do one or both of the following:
- Have thin sections where you know the identity of the minerals so you can compare with your unknown, on exactly the same analytical conditions.
- Get access to an EDS-SEM system. I know it's easier said than done, but nowadays these instruments are extremely common in almost every research institution, and once you're experienced it takes literally minutes to identify the minerals.
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$\begingroup$ thanks @Gimelist you are right, there are two ore minerals- pyrite and chalcopyrite. $\endgroup$ Feb 25, 2020 at 13:01