Questions tagged [rocks]
Questions about rock types, formation, chemistry, and physics.
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Mud cracks formation
Are mud cracks formed during rock formation or after the rock is completely formed?
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Identifying dense magnetic rock with tubular features [closed]
I recently found a few rocks scattered in a valley, without any clues about where they may have come from (they did not look anything like the local soil, rocks, or layers of rock that could be seen ...
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Is there a theoretical maximum size limit for a rock?
There are many types of rocks: igneous rocks, sedimentary rocks, and metamorphic rocks. Some rocks are simply huge. Some of them are tiny. Is there a theoretical upper limit on the size of a rock, and ...
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Why does calcium occur together with felsic rocks and magnesium with mafic rocks if calcium is denser than magnesium?
Felsic rocks contain a lot of sodium, potassium and calcium (and a great deal of aluminum), while mafic rocks consist of a lot of magnesium with iron....
Why is this?
Why is magnesium (z=12) in the ...
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Identify source of rings pattern in flint
This stone was found at the beach on the Danish side of Øresund (Amager strand in Copenhagen). I believe it is flint, though I am not sure. There is a pattern of rings on one of its sides (see photos)....
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Hexagonal phenocrysts with a metallic luster?
I recently realized that I am surrounded by interesting rocks. Having no background in geology nor geologist friends, I rely on online resources to navigate the intriguing stuff I stumble across. But ...
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Are rocks extracted from deep drilling, brittle due to pore pressure?
When a saturated rock sample is rapidly extracted from a place with high water pressure, as happens in oil drilling or deep mining, the water is trapped inside the rock at high pressure, trying to ...
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Why does the sandstone in Yehliu and other scenic coastal northern Taiwan look like vanilla fudge swirl ice cream?
I had the photos below handy from a recent trip, but in other areas of northern taiwan you can see very long, thin sheets of this dark, rust-like "chocolate swirl" separating very large, ...
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Are river rocks and stones a renewable resource?
Imagine the polished / unpolished rocks and stones that people use to decorate their homes and gardens.
Are they a renewable resource? Are there plenty of them?
If we give 200 pounds of them to each ...
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On QAPF (Steckeisen) diagrams, should Albite be considered on the Alkali feldspar or Plagioclase side? Or in-between?
QAPF diagrams are double ternary diagrams used for magmatic rock classification based on mineralogy.
Quartz and Feldspathoids are opposed on the pointy ends of the diamond, with Alkali feldspar and ...
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Geology of the San Gabriel mountains in the Angeles national forest - rock types
I'm not a geologist, I am a hiker. And after many hikes in California's Sierra Nevada and Utah's red country I figured it would be great to learn some geology and I'm just posting this question to see ...
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Why does fracturing occur along a specific plane or region of the rock?
In this typical image of rock fracturing, why do the joints / fissures occur where they do, as opposed to, say, along the line drawn in blue on the image? More specifically, what characteristics of ...
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Patterns on Basalt
These Basalt rocks were hand cracked and used to build the walls on my home.
Many of these rocks have these semi circular pattern, made of the basalt itself. It's just a bit darker than the rest of ...
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What is the "healthiest" rock?
When talking about rocks, i.e. an aggregate of minerals, which type would be the "healthiest"
I'm not talking about some voodoo crystal-healing stuff here, just if there is any rock ...
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Igneous and Sedimentary Rocks' Susceptibility to landslide
Which is more susceptible to landslide based on lithology compared to one another?
Granite, Conglomerate, Sandstone, Mudstone
I've been tasked to create a hazard map and was given a Geologic Map, ...
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Internal rocks in glaciers
I am very new to the study of the cryosphere. I was looking at the GLIMS inventory for glaciers and observed red patches as shown below which the legend mentions the red patches as internal rocks. In ...
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Looking for Rock/Mineral Identification Flowchart
As a christmas present, I bought a box of minerals/rocks for my girlfriend, who recently got interested in geology. Unfortunately, she could not attend the identification class in university. The box ...
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Why is felsic (granitic) lava so much more viscous when flowing (or trying to) than mafic (basaltic) lava?
A lower average temperature is, apparently, only part of the answer....
Several sites said composition, not temperature, explains most of the difference...
And the difference in viscosity can be up to ...
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Why is the inner core about 85% iron and the rest (mostly) nickel, while the outer is roughly 80%/20%, if nickel is denser than iron?
The question is basically the title. I really cannot think of a good reason. Is it a mystery to geologists?
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Where to find graphite rocks? [closed]
Where to find graphite rocks?
I made researches in my city beach but I don't know where to find them.
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What is the sedimentary form of gabbro/diabase? What would it look like?
Gabbro is an intrusive, mafic, and igneous rock. How would it turn into sedimentary rock?
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Are there any rock recognition practices or games?
I'm a complete beginner in fossil collection but from my understanding I should mostly look at sedimentary rocks for fossils. However the problem is that rocks that I see in real life are not the same ...
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How did these holes form in the rock? [closed]
I've been trying to figure out how these holes formed in the rock. These pictures were taken in Quebec, Canada on small lake in cottage country. The strange thing is that they are almost both ...
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Does water affect radiometric dating?
When radiometric dating, would water affect the measured age of old rocks ?
Specifically would water affect Uranium-238 to Lead-206 dating of Zircon crystals?
Would it affect the lead since it’s ...
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Are we observing sedimentary rock formation today?
For instance, are we able to see the microscopic accumulation of shale or limestone?
Can anyone reference me to sandstone formation observation, that would have to occur more rapidly. I’ve heard it ...
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What is this fossil found in flint in Kent?
My 7 year old son found this fossil whilst cracking open flint in Deal, Kent.
The fossil (assuming it is) looks like scales/cells/shell and is chalky. The oblong lines are raised and well defined and ...
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What kind of rock is this? [closed]
A few years ago in Venezuela, parque nacional de Cainama, the tourist guide found and gave me this rocks, he told us that a geologist told him that those could be radioactive but no one believed him. ...
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How did this stone become encased within different rock?
My father, in his younger years, was a stone mason in Cincinnati Ohio. A couple of decades ago he was building a wall of some kind. He would fetch rock from a creek bed, haul it to the construction ...
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Prevalence of 'well-rounded' beach fabric on the Foreshore
Apologies for the vagueness of this query, but generally, would it be plausible to state that the prevalence of 'sub-rounded'* beach fabric is more common at the foreshore than 'sub-angular'* beach ...
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How to identify chemical property and structure of rocks?
I am interested in identifying the properties of rocks. For example, black opal is shiny and can emit 5 different colors based on different lighting conditions. Is there a way for an amateur to be ...
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Ore Deposit Identification
What type of ore deposit does this rock best represent?
A rock with a porphyritic texture is cross cut by a stockwork of
quartz veins. Bordering the veins is extensive alteration of the host
rock. ...
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Feldspar content of coarse-grained igneous rocks
From the chart, I would say that plagioclase feldspar is more abundant in coarse-grained igneous rocks than alkali feldspar, as it is found in all three listed, whereas alkali feldspar is only present ...
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Arabian Desert rock formation
I'm interested about this rock formation in Arabian desert. The rock looks like melting chocolate.
Not sure where the exact Location, the source says it around Al-Ula, Saudi Arabia. Here the image ...
user21860
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How is it possible for rocks to be trapped within another type of rock?
More specifically, I would like to know how the rocks in these pictures have formed:
If this is because magma has melted and trapped the other rocks inside, do they have a different melting point ...
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What causes dye to bleed from an agate stone?
I came across this review on Amazon. The cold drink was placed on top of the agate stone and the dye bled and left a permanent mark on the table.
Why does this happen? Is it because of the ...
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What's eating this sandstone
I decided to remove the tiles in my front courtyard and turn it into a garden of succulents. After removing a couple of rows of tiles then digging into the soil, I started seeing a strange thick ...
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How would one go about drawing the contour lines for this map in order to draw the cross section?
Good Day. We Received this map as practice for our Geology university module and I have no idea how to draw the strike lines where the different heights intersect the different rock types in order to ...
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Lamé parameters of granite and similar rocks
I am looking for a book or an article where I can find the Lamé parameters of Granite, any help would be appreciated.
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What is this red glassy rock [closed]
I found rocks looking like this in my backyard but cant get to know what they are or how to find out. Below are pictures
I don’t know if there’s more info I should mention. If there’s anything please ...
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Why does radioactive dating work on specific rocks?
As I understand it, radioactive dating measures time by what portion of a radioactive isotope has decayed. Weren't all the natural radioactive isotopes created during the formation of the solar system?...
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Megaspherulite growth
I have been fascinated by photos of these for a while, and I would like to ask how megaspherulites grow so large, when spherulites are normally quite small?
I also noticed that all papers about the ...
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Why aren't there ultra acid igneous rocks?
In my study, I found that in volcanoes when the magma is going up it formed different types of rocks. There are basic, acidic and ultrabasic.
My question is why isn't there ultra acid igneous rocks ...
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Using Enhanced Rock Weathering in the Sahel Region of Africa
A recent Guardian article "Spreading rock dust on fields could remove vast amounts of CO2 from air" has gotten some attention in the nongovernmental and UN organizations working in the Sahel ...
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Is there a modelling of Wave Rock (Hyden Rock) formation?
I'm interested in the visualization of the formation process of "strange" objects like Wave Rock (flared slope). I've found articles describing hypotheses of the rock formation but I cannot ...
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When Earth formed 4.5 × 10⁹ years ago, how much radiation did surface rocks emit?
When Earth formed $\approx 4.5 \times 10^9$ years ago, Earth's surface rocks emitted more radiation because they had more unstable isotopes. All short half-life isotopes decayed long ago, and the ...
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What is the time period of these chalk/clay layers?
These limestone-clay rocks are very common in the Alps, they come from weather changes.
How many years does it take to make one of the rock bands? 7 years, equivalent to an el-nino type event? 1000 ...
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Non-invasive techniques to find rock composition
If we had access to a totally new kind of rock (maybe a new meteorite), is it possible to tell what the rock is composed of without touching it / drilling into it?
I'm thinking of something like ...
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In radiometric isochron dating why is at t=0 D*/Dref=const but P/Dref not?
I am a physics graduate and trying to understand one of the assumptions made for isochron dating of rocks: at crystallization time of the rock, $t=0$, the ratio of the parent isotope to a stable ...
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Use of radiolarian fossils to assess CO2 levels in early geological periods
Radiolaria are microscopic marine protozoans commonly found as fossils in rocks dating as far back as the early Cambrian. Their silica skeletons are damaged by high levels of CO2, so is it possible to ...
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Sources or strategies for stone identification
I have a bunch of semi-precious stones here, but I am not very learned in geology etc and I would like to have some way to know what kind of stones they are. As far as I understand question about ...
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