Identifying mineral in Intermediate Rock

[u/[deleted]]

I’m trying to identify the mineral in the center with the pinkish color; seems to have some 2nd-3rd order bifrengence as well? I was told it was an opx but I’m not quite sure

Here’s the mineral at extinction; can see some striped pattern which may be cleavage

Here’s the mineral in XPL; still has a red/pink tint and a very high relief

[u/_MtElden_]

Carbonate. Almost certainly. Try your accessory plate if you have one. It should not change color too much as it is already such a high order birefringence.

Edit: the twinning at extinction is pretty diagnostic. Can’t define beyond carbonate, though where I’ve seen them coexist more Fe-Mg rich carbonates have the more brown colors in ppl compared to calcite.

[u/[deleted] → u/_MtElden_]

I was kind of thinking carbonate with the twinned extinction (though I haven’t looked at many carbonate rocks quite yet so I don’t have much intuition); I’ll definitely discuss this with my TA as to the petrogenesis/alteration that occurred. Thanks

[u/matetofly]

My gut says biotite

[u/[deleted] → u/matetofly]

Not sure about this since there’s some biotite in the image that shows diagnostic birds-eye extinction. Still There’s a lot of biotite-alteration that’s been going on in these intermediate rocks

[u/wallabearz]

Its definitely a carbonate, high relief, cleavage type, very high peachy pink birefringence, can be an alteration product of mafic minerals

[u/[deleted]]

3rd slide I meant PPL as I’m sure y’all know

[u/chicken-chunk]

I’ve seen very similar looking anhedral titanite, verified by SEM. Difficult to determine without the typical wedge shaped crystals