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Re: Rocks and Minerals B/C

Posted: September 28th, 2017, 3:28 pm
by ScottMaurer19

That appears to be right to me. I think you can just ask the next question if you'd like.
[img]https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT3HP4C2YvRvVihQX8T0087wVTkO6-wRKnCG6T7KkX7SWPx0rpK[/img]
1. What is the rock?
2. What is the mineral?
3. Name the area where the rock is most commonly found.
4. What is the rock's plutonic equivalent.
1. Looks like a really bubbly basalt, even edging into scoria
2. Olivine
3. Basalt is a very prevalent rock in oceanic crust and mafic lava flows. Scoria is found as bombs and tephra from volcanic eruptions.
4. Gabbro
Probably vesicular basalt

Re: Rocks and Minerals B/C

Posted: September 28th, 2017, 3:47 pm
by dxu46
[img]https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT3HP4C2YvRvVihQX8T0087wVTkO6-wRKnCG6T7KkX7SWPx0rpK[/img]
1. What is the rock?
2. What is the mineral?
3. Name the area where the rock is most commonly found.
4. What is the rock's plutonic equivalent.
1. Looks like a really bubbly basalt, even edging into scoria
2. Olivine
3. Basalt is a very prevalent rock in oceanic crust and mafic lava flows. Scoria is found as bombs and tephra from volcanic eruptions.
4. Gabbro
Probably vesicular basalt
It's vesicular basalt. whythelongface, your turn!

Re: Rocks and Minerals B/C

Posted: September 28th, 2017, 7:16 pm
by whythelongface
[img]http://www.alexstrekeisen.it/immagini/diagrammi/feldspar.jpg[/img]
1. What is the unlabeled region in this triangular plot known as?
2. What is the difference between orthoclase and monocline?
3. Under a polarized thin section, what is the easiest way of differentiating plagioclase, monocline, orthoclase, and quartz?

Re: Rocks and Minerals B/C

Posted: September 29th, 2017, 12:46 pm
by OrigamiPlanet
[img]http://www.alexstrekeisen.it/immagini/diagrammi/feldspar.jpg[/img]
1. What is the unlabeled region in this triangular plot known as?
2. What is the difference between orthoclase and monocline?
3. Under a polarized thin section, what is the easiest way of differentiating plagioclase, monocline, orthoclase, and quartz?
1. High temperature compositional region?
2. Orthoclase lacks lamellar twinning whilst microcline does, and microcline is the only one that can be in a darker color/blue-green.
3. Look for cleavage: If it lacks cleavage than it is likely quartz. I'm not sure with plagioclase, monocline and orthoclase other than the color composition.

Re: Rocks and Minerals B/C

Posted: September 29th, 2017, 2:04 pm
by whythelongface
[img]http://www.alexstrekeisen.it/immagini/diagrammi/feldspar.jpg[/img]
1. What is the unlabeled region in this triangular plot known as?
2. What is the difference between orthoclase and monocline?
3. Under a polarized thin section, what is the easiest way of differentiating plagioclase, monocline, orthoclase, and quartz?
1. High temperature compositional region?
2. Orthoclase lacks lamellar twinning whilst microcline does, and microcline is the only one that can be in a darker color/blue-green.
3. Look for cleavage: If it lacks cleavage than it is likely quartz. I'm not sure with plagioclase, monocline and orthoclase other than the color composition.
Admittedly this was a bit harder than usual.
1. The answer I was looking for was "Miscibility gap". This is a region on the triangular plot where no solid form of the chemical composition described there exists. In other words, there is a gap in mixing of different endmember elements.
2. Yes, but I was thinking of something more general, as in formation. Microcline is formed from the slow cooling of alkali feldspar species. It is also triclinic as opposed to microcline, which is monoclinic.
3. Under a cross-polarized microscope, one can readily see vertical lines in plagioclase minerals - that's because it twins following the albite law. Orthoclase crystals have more horizontal cleavage, which is also easily spotted. Microcline will usually have a grid-iron pattern of scratches on crystal surfaces. Quartz is more uniform, has a weaker and often undulatory birefringence pattern. What this means is that the extinction of cross-polarized light is not very apparent when you rotate the crystal.
Your turn.

Re: Rocks and Minerals B/C

Posted: October 3rd, 2017, 12:40 pm
by OrigamiPlanet
1. Phenocryst
2. Vitreous
3. Vesicle
4. Cleavage
5. Twinning
6. Peat

Re: Rocks and Minerals B/C

Posted: October 3rd, 2017, 2:24 pm
by dxu46
1. Phenocryst
2. Vitreous
3. Vesicle
4. Cleavage
5. Twinning
6. Peat
1. a crystal on a rock that is especially conspicuous
2. glassy or looking like glass
3. air pockets
4. a sharp division
5. two or more crystals forming within each other.
6. the lowest grade of coal, with lowest carbon concentration

Re: Rocks and Minerals B/C

Posted: October 3rd, 2017, 9:12 pm
by whythelongface
1. Phenocryst
2. Vitreous
3. Vesicle
4. Cleavage
5. Twinning
6. Peat
1. a crystal on a rock that is especially conspicuous
2. glassy or looking like glass
3. air pockets
4. a sharp division
5. two or more crystals forming within each other.
6. the lowest grade of coal, with lowest carbon concentration
I'd make the following corrections:
4. Cleavage is the way the atoms in a crystal split along weaker surfaces.
5. Multiple crystals in different orientations, sharing a common surface
6. Peat is the precursor of coal, it is organic matter that has not yet been metamorphosed.

Re: Rocks and Minerals B/C

Posted: October 4th, 2017, 12:48 pm
by OrigamiPlanet
1. Phenocryst
2. Vitreous
3. Vesicle
4. Cleavage
5. Twinning
6. Peat
1. a crystal on a rock that is especially conspicuous
2. glassy or looking like glass
3. air pockets
4. a sharp division
5. two or more crystals forming within each other.
6. the lowest grade of coal, with lowest carbon concentration
I'd make the following corrections:
4. Cleavage is the way the atoms in a crystal split along weaker surfaces.
5. Multiple crystals in different orientations, sharing a common surface
6. Peat is the precursor of coal, it is organic matter that has not yet been metamorphosed.
dxu46, you are still right to an extent, but I would prefer whythelongface's response with the last three as they are more accurate.

Re: Rocks and Minerals B/C

Posted: October 7th, 2017, 6:01 pm
by whythelongface
New question:
1. What is the defining characteristic of sedimentary rocks in a low-energy environment of formation?
2. What is SEDEX?
3. From what mineral does Kaolinite form from?
4. What is a metamorphic facies? Give an example.
5. Explain fractional crystallization.