Questions tagged [petrography]
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.
6
questions
4
votes
1
answer
62
views
Help with petrographic analysis of a complex mineral
While performing petrographic analysis in a rock composed mainly of plagioclase, pyroxene and olivine, I came across the mineral shown in the photo. Do you have any clues of what it could be?
The ...
- 41
2
votes
1
answer
56
views
What would a rock thin section look like without any polarizers?
I'm interested in knowing what features can still be discerned.
I've been struggling find any image of a thin section of a rock under a regular light microscope, or a petrographic microscope with the ...
- 23
2
votes
1
answer
141
views
What do opaque rims on biotite in a volcanic rock mean?
In a volcanic region, i have examined two samples petrographically. One of them has biotites with extensive opacitic rims. The other samples biotites hasn't got this property. They have the same modal ...
- 889
4
votes
1
answer
367
views
What is the maximum grain size of a sediment that can be point counted using a standard thin section?
Point counting is an extremely useful tool for determining the composition of a clastic sedimentary rock. It is also very useful in provenance studies to determine the sediment source of a sedimentary ...
- 316
6
votes
1
answer
143
views
Identifying trichroic crystal systems
An unknown mineral shows three distinct pleochroic colours. Explain what observations you need to make in order to decide which crystal system it belongs to.
If it has three pleochroic colours this ...
- 2,211
8
votes
1
answer
2k
views
How are spherulitic structures formed in basalt rock?
After having studied the thin sections of basalt under the microscope, I have come across many spherulitic structures occurring in clusters.
How can this happen?
Is it due to devitrification or is ...
