The view is from an Alkaline biotite granite. I attach photographs of varying magnification to give a clearer view. The halos around rims chloritized biotite is thought of be of zircon or monazite (or can it be xenotime?) and inclusions within sericite of feldspar?. Also, the Fe-oxide was opaque in transmitted light. However, I wonder why the presumed zircon grain had high reflectance like Fe-oxide minerals under reflected light microscopy.
The high relief, high birefringence in TL coupled with reflectivity under RL, probably imply the mineral grain could be titanite/ sphene which will be also radioactive in some of the granitic rocks.
Zircon should not have a very high reflectance in polished sections. Hence, it is probably titanite. Are your Fe-oxides all opaque? Usually, they have some internal reflexes (reddish = hematite; brownish = limonite).
Thanks so much Daniel Müller . Now I am sure it is titanite. I have other varieties of Fe-oxides too.
Asoori Latha thanks. It is titanite. Some Fe-oxides are brown
Dear Kayode: it is not easy to identify minerals in static photos, at least you should annex a photo with the mineral in a position of maximum illumination under crossed polars, so that its birefrigence can be seen properly. All the pictures show the mineral at extinction. I don't think it is titanite, it seems to have inclusions of brown titanite, but that crystal is probably something else. The extinction shown is oblique so it cannot be zircon, but it could be monazite. These peralkaline rocks are known to contain some rare species, so it won't be easy to identify some of them... Please send a picture at maximum lillumination!
Regards, Sebastián.
No, sphene is not pseudoisotropoc it is a very high birefringence mineral, pseudoisotropic could be perovskite and othee tare metal oxides, some melanites also can be pseudo isotropic. Regards, Sebastián
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