December 4, 2017
Monday Geology Picture: Garnet Biotite Tabletop
Posted by Evelyn Mervine
Red garnet and black biotite… in a tabletop! South African coin for scale.
Since re-starting my blogging, I missed a few weeks of weekly pictures. My apologies! Life with a newborn does not leave much extra time, I’m afraid! I’ll try to be more consistent with my blogging in December and going into the new year.
However, I have a great picture for today: a close-up snap of a lovely stone tabletop that I recently saw, believe it or not, at a McDonald’s here in Cape Town — the one near the stadium downtown. You can see some beautiful minerals in this particular tabletop: garnet, biotite, feldspar, and quartz. The dark red garnet and black biotite stand out in particular.
The tabletop was really lovely, with some light and dark gneissic banding.
Here are a couple more views:
Another view of the tabletop.
One last view of the tabletop.
Thank you for the useful information in your blog.
I am working in a stonework contracting company. It seems some gneiss group stone (which is normally classified as ‘granite’ in our industry) usually contain garnet, such as Santa Cecilia (Brazil), Giallo SF Real (Brazil), Kashmir White (India) [sorry that I do not know how to upload photo]. Is garnet formation associating with the metamorphic process or garnet occuring is just ingredient of protolith before metamorphism?
As learnt from your blog (thank again!), under the Bowen’s Reaction Series, pyroxene / olivine (gabbro/basalt) formed before potassium feldspar / quartz (granite). However, garnet can be found in some types of basalt and granite. Is formation of garnet in igneous rock independent to the Bowen’s Reaction Series?
Thank!