Questions tagged [rocks]

Questions about rock types, formation, chemistry, and physics. If you just want help identifying a rock please use the tag "identification-request".

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1answer
77 views

What ore minerals are likely to be found in a thin section like this? What can we deduce from the structure?

The following image is of polished sample of mineral-rich rock. There are two major portions we can see that is ore minerals and rest the grayish material is gangue. The photo was taken with an ore ...
3
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1answer
163 views

How does this melted-wax erosion pattern form in sandstone?

How does this kind of erosion pattern that looks like melting wax form in sandstone? Can you describe the kinds of processes and kinds of rocks that are needed for this? I've seen it in Nevada, but ...
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1answer
204 views

Differentiate a rock and mineral

How to differentiate between a rock and a mineral by merely looking at it as a thumb rule?
3
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1answer
169 views

What kind of rock or stone is this? Where did it come from? [closed]

I found this on the side of the road in Oregon, i think it was left or forgoten about thats why it was left there but it has crystal pockets, multiple colors, some smooth sides, perfect circles and ...
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1answer
111 views

The differences in gases produced by asteroids impacting crystalline and sedimentary rocks

A second question inspired from How Long Will Life Last On Earth, The Manicouagan crater in Canada is one of the largest impact crater on Earth. It was created 215 million years ago, but its ...
3
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1answer
65 views

Energy Density of Porous Rocks

It's very long, I know. But please, don't be discouraged from going through this question if you can help me. The question is at the second to the last paragraph, but you need to read through to ...
3
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1answer
33 views

Marks on boulders of volcanic origin

I am working in a catchment in the southern Ecuadorian Andes, about 3700 m.a.sl. Rock outcrops at the upper part of the catchment, as massive blocks varying their size from one meter up to five meters,...
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2answers
1k views

what is a transverse isotropic rock?

I know isotropic means equal properties in all directions , but the term "transverse" is not making it easy for me to understand.
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322 views

Puzzle using relative dating principles

This isn't directly looking at a real life ecological example kind of thing, but it requires knowledge of relative dating, so I thought I would come here. Here is what was told: -"Worms" (curved ...
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130 views

How Common is Volcanic Tuff?

Volcanic tuff was a key material in the Roman invention of concrete, something that modern concrete, or "Portland cement", lacked. With tuff, not only would Roman concrete be waterproof, it would ...
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49 views

Link between different ways of modeling permeability

The most famous equation describing the permeability $k$ of a soil is the Kozeny-Carman equation: $$k = \frac{\phi}{8}r^2 \approx \frac{\phi}{c}\left(\frac{V}{S}\right)^2$$ $\phi$: porosity V: pore ...
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3answers
699 views

What is meant by intraplate volcanism?

I am having massive confusion on whether intraplate volcanism refers to volcanism occurring at plate boundaries or away from plate boundaries (such as formation of ocean island basalts), or perhaps ...
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3answers
229 views

A human foot impression on a rock

There is a rock that I have been climbing ever since I was a kid to get a magnificent view of an escarpment. One of the things that was part of our rock tour among other things was a perfect human ...
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1answer
35 views

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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3answers
118 views

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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1answer
181 views

Ions & elements, which is the correct terminology to use when discussing chemical compounds in Earth Science?

Different textbooks use different terminologies when discussing the same chemical compounds, for example when discussing the minerals... Elements / Compounds Sulfide minerals consist of metallic ...
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1answer
449 views

Inorganic Limestone and Inorganic Gypsum

I read that limestone is made from the compaction of marine animals' bones. But, I am unable to find out why limestone could not have been produced from calcium occurring naturally (5th most abundant ...
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49 views

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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0answers
44 views

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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1answer
42 views

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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34 views

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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0answers
25 views

Faster shale velocities in deviated wells

I am currently working with sonic measurements in the wells and there is an observation, that velocities are faster in shales over the deviated parts of the well. So, when the relative dip between the ...
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0answers
26 views

What would create the triangles in this rock I found in the Lehigh River [closed]

I collect rocks from the Lehigh Valley River, I have found some many interesting rock. With details that could not be from the water. Can you tell me what would cause the 3 triangle indents on this ...
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70 views

Whats this stone? [closed]

Found it couple days ago and it amazes me how smooth the surface is but cant identify it please help me. Found it in north germany near a lake on a trip there.
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541 views

How are natural specimens, such as ‘Moqui Marbles’, distinguished from man-made artifacts?

If a particular type of rock specimen is found throughout Earth and is made entirely of natural minerals, but the individual specimens differ minutely from another in size and shape and look to be ...
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1answer
103 views

What kind of purple stone is this? [closed]

I found this stone and I do not know what type of stone is this?
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4answers
555 views

What is this Lake Michigan rock? [closed]

Rock found along northern Lake Michigan, (Charlevoix, MI). Made up of very thin crystalline layers. There are small, round bubble like bumps that protrude from the surface. Doesn't show well in the ...
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2answers
60 views

Chloride ions for the salty seawater

Where does the chloride ions that are required for the salty taste of sea water come from ? I know that it is the weathering caused by the slightly acidic (due to dissolution of CO2 with water) rain ...
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1answer
239 views

How can I tell the difference between granite and syenite?

(I'm not a geologist, just helping my kids collect rocks).
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1answer
1k views

Is this platinum ore? [closed]

Was found in central Mexico. It's very metallic, shiny, showing some streaks of gold and quartz.
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1answer
28 views

Why don't pyroxenites and peridotites appear in Streckeisen's QAPF diagram?

Wikipedia says for QAPF diagrams: "A QAPF diagram is a double ternary diagram which is used to classify igneous rocks based on mineralogic composition." Why don't pyroxenites and peridotites ...
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1answer
528 views

Oldest to Newest Bedrock in the USA “road trip”

I am supposed to design a road trip (using major highways) across North America. I have to design a route that starts with the oldest rock of Archean age and finishes with the youngest rock of ...
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2answers
737 views

Does grade of metamorphism apply to igneous and sedimentary rocks?

Does grade of metamorphism apply to igneous and sedimentary rocks? I know that grade of metamorphism applies to the scale in which a rock becomes crystallized. Or is it? Please also define grade of ...
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1answer
256 views

Why do manganese nodules have different constitution than sea water?

Analysing the constituents of manganese nodules, we find that the relative proportion of minerals differs from that of the surrounding sea water. Can someone explain to me why the proportion of the ...
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1answer
37 views

How to calculate or find the compressional stress wave velocity, Cp for a rock

In Cunningham's paper, "The Kuz-Ram fragmentation model - 20 years on", he makes mention of compressional stress wave velocity, Cp. He only comments that the Cp of granite = 5.2 km/s. I using a ...
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1answer
60 views

Help identifying rock? [closed]

Found in stream, heavy, has a tin of red lines and dark. 1]]2[grey white, rusty ]3. Dark lines n rusty lines. Hard to break off piece ain't magnetic
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1answer
71 views

What type of mineral is this? [closed]

My grandfather found this thing.
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0answers
88 views

How can I find out if this is a geode without breaking it in half? [closed]

I found this rock today on my property. It looks similar to another rock I saw that was said to be a civil war cannon ball, however comments below suggest that it could be a geode. Are there any ...
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0answers
93 views

What a place that sells rocks is called [closed]

If a nursery sells plants, I'm wondering what a place that sells rocks is called. Something where they offer rocks of various sizes like this: Well, those are all river rocks, but I'm wondering about ...
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3answers
391 views

Can anyone help me identify these rocks please? [closed]

I apologize for any errors in my pictures or writing. My first post. [
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0answers
56 views

Identifying rocks, minerals [closed]

I am sorry to bother you.. before passing away, my grandfather gave me a special box that contained all types of beautiful, colorful rocks and minerals. I am having a hard time identifying them! Could ...
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0answers
70 views

Rock / Fossil ID? [closed]

Please see link below if anyone can help ID. I think the little claw looking thing is a fossil? The red rock is smooth,Matt in some places and semi glossy on some of the sides. The black rock has ...
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0answers
96 views

I found this rock on Laguna Beach [closed]

Rock found on Laguna Beach. It is not sand stone and is heavy for its size 3" x 2". It is rather dense. Click the image for full size:
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0answers
76 views

I was wondering if anyone could help me identify this rock [closed]

I found this rock along with a few other very similar ones. I found it on an island in Croatia.I was wondering if anyone could tell me the name of the rock.
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0answers
74 views

classification of oil shale

Could we classify oil shale as a biochemical sedimentary rock ? Oil shale is a muddy rock contains Kerogen. So I think in oil shale to be a mixture of Kerogen and mud sediments, and that's not the ...
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0answers
46 views

Weathering of silicates

I am trying to find a relationship between the silicate-rich rocks weathering products. For example I've found information regarding gabbro weathering in which, according the consulted source, in 100 ...
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0answers
435 views

What does a negative value for the inclusive graphic standard deviation mean?

I'm calculating the inclusive graphic standard deviation for sediment from a cumulative frequency graph, with this formula: But when I plug in the numbers, I get a negative value, because my ranges ...
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3answers
997 views

If rocks are stones, what type of rock are gallstones? [closed]

From Wikipedia: Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a common rock, is a combination of the minerals quartz, ...
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1answer
596 views

The rock that gives birth to quartz sand

Thanks to one minute of the Earth we know that beach sand mother rock, besides the quartz itself, is (or was?) made of olivine, amphibole and orthoclase. I wonder, what is the name of that rock and ...
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1answer
2k views

How long will it take for the ocean to erode Rockall?

Loosely related to the question Will the ocean eventually erode all land?: How long will it take for the ocean to erode Rockall (an uninhabited granite islet within the exclusive economic zone of the ...