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Results tagged with petrography
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user 725
Petrography is the science of observing and interpreting textural relationships of minerals and other features in rocks as observed through thin sections using an optical microscope.
1
vote
Accepted
What do opaque rims on biotite in a volcanic rock mean?
There are several options.
During decompression, biotite is no longer stable and the hydrogen volatilises, leaving behind fine-grained intergrowth of oxide and silicate minerals.
Oxidation of the ri …
- 23.3k
3
votes
Accepted
What would a rock thin section look like without any polarizers?
It would look almost identical to the image obtained using plane-polarised light.
Some minerals would look darker, especially those with strong pleochroism such as biotites and amphiboles, because al …
- 23.3k
1
vote
Accepted
Identifying trichroic crystal systems
Theoretical answer:
You need to measure extinction angles. If it is always extinct when aligned to cleavage or crystal faces, then it is orthorhombic. If it sometimes aligns and the colour is consist …
- 23.3k
7
votes
How are spherulitic structures formed in basalt rock?
According to the image that you provided, what you are seeing are not spherulites, but rather epoxy bubbles. More on that later. I will first answer what are spherulites:
Spherical features observed …
- 23.3k