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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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What are the most common minerals at the Earth's surface?

I know how to find out the first few most common minerals, and I know how to find a list of 6800 minerals that one geologist found as a microscopic grain in this one meteorite. I can't seem to find a ...
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1answer
741 views

What are these oblong shaped rocks called, with pigment inside? [closed]

There are these rocks we have -- not too common, usually find them in loads of small rocks, very seldom at random. They are perfectly oblong, and sort of smooth, but not quite as smooth as a river ...
4
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1answer
421 views

Any idea what are these circular rock marks?

During a family trip in the Israeli National Trail in the Pora Stream part (31.496871, 34.770928), I noticed these circular rock marks. Any idea what are they?
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1answer
167 views

Is this a rock? [closed]

My son found this in our front yard. We live in Richardson, TX. It is brittle and little gold flecks fall from it when you handle it. The darker smooth parts are like a mirror. The clear part at the ...
4
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1answer
829 views

How to find rocks worth tumbling?

My son recently got a rock tumbler and I was wondering if anybody knows of any resources that would show pictures of the different types of rocks as they would be found on the ground. I live in Chino ...
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1answer
147 views

Can anyone identify this stone? [closed]

I found this rock at the weekend in the forest of Haigh Hall, Standish. It seems to be a solid mass of fibrous material. I have given it a scrub with warm water and a toothbrush just to get rid of ...
4
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1answer
180 views

Why pro-gradation occurs along coastal environments?

I am currently studying the deposition process in coastal environments and I came across a point which I do not understand concerning grading of grain size. According to "Petroleum Geology by North F....
4
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1answer
190 views

Why would CaO be more finely spread than K2O in Granodiorite?

I recently interpreted some XRF data on samples of a granodiorite which were classified under three different types of physical characteristics: very little, mild and significant levels of weathering. ...
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572 views

Definitive values that classifies a rock as having “low”, “medium”, and “high” -strength, -hardness, -toughness, and -consolidation?

Question: Are there any widely accepted published values (or ranges) that classifies a rock as having “low” “medium” “high” -strength, -hardness, -toughness, and -consolidation (cementation or ...
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4answers
3k views

When metamorphic rocks undergo pressure, how are they changed?

When metamorphic rocks undergo pressure they are changed, but how are they changed? Do they become fragments of rocks? Doesn't that mean that the difference between sedimentary rocks and metamorphic ...
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2answers
1k views

Radon is a naturally occurring radioactive gas. How does this work?

Radioactive rocks can release a gas called radon when they decay, which can build up in the basements of buildings with serious effects on people's health. Does anybody have information on how radon ...
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2answers
107 views

Odd Inuksuk-like objects

I found some huge objects that are way too big to be inuksuks, in my opinion. The object on the right is very odd because the arms are not straight like they are in most images of inuksuks. and ...
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2answers
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I found this strange spherical stone in Gillette Wyoming. I have no idea what it is. Please help. [closed]

These are recent pictures of it. It’s heavy, I see small minerals that catch the light in it, very bumpy, spherical, doesn’t seem to be magnetic, I was falling down a deep trench and kicked it up at ...
3
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1answer
89 views

What is this rock I found being sold in a store? [closed]

I was recently on vacation in Hawaii and while there, entered a rock and mineral type store where I saw the rock below. I forgot to ask what it was while I was there and I am unable to go back and do ...
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2answers
269 views

A few questions about glass

A glass, as I understand it, is a material whose solid phase is amorphous and which undergoes a glass transition when heated. My train of thought - and therefore my questions - began with obsidian. ...
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2answers
658 views

Rock identification: opal or crystal? [closed]

I picked this up from a good friend, he didn't have any information but someone said it was an opal and not a crystal. It is see-through like foggy glass in some spots. hardness rated as quarts size ...
3
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1answer
940 views

What's the difference between cleavage and fracture?

I see both terms refereing to fractures on crystals or minerals, so I wonder if they could be considered synonymous. If no, what's the difference between both terms?
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1answer
698 views

What is the difference between subvolcanic rocks and plutonic rocks?

I'm studying Plutonic (Intrusive) rocks and I really don't understand the difference between Plutonic Rocks that form in Sills and Dikes from the so called subvolcanic rocks, also known as a ...
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5answers
835 views

Where are the oldest igneous rocks found?

I'm trying to catch up on my homework for earth science, but I'm having a difficult time searching for an answer to my question.
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2answers
101 views

I don't know what this rock is [closed]

I got this rock a year ago at a mineral and fossil event, and there was a stand where they where selling 'mystery packages', boxes full of different fossils and minerals. I bought one, and figured out ...
3
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1answer
592 views

Does flow banding only occur in silicic rocks?

I made a video about what I learnt in my A Level Geology course so far, about igneous rocks. One thing I mentioned was that flow banding is mostly only found in silicic rocks (and so mostly rhyolite) ...
3
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1answer
137 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
187 views

Differentiate a rock and mineral

How to differentiate between a rock and a mineral by merely looking at it as a thumb rule?
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2answers
739 views

What is this white rock with black speckles throughout? [closed]

I was wondering if you have any ideas on what kind of rock this might be? I know that it doesn't effervesce with HCl (no reaction with hydrochloric acid at all) and the size and shape of each grain is ...
3
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1answer
753 views

What kind of rock is this? [closed]

We found this today in Acton CA USA. Would like to know what it is.
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2answers
388 views

Growth identification on obsidian needed [closed]

What are the small white growths on my obsidian? And does this specimen look odd or rare?
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1answer
121 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
110 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 ...
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1answer
32 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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1answer
329 views

heavy, brown, rock with crystals, please help identify [closed]

please help identify this rock. it is heavier than most. dark brown color. picture is shown with streak test. found in Philadelphia pa. at home demolition site. crystals seem to be different type and ...
3
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1answer
171 views

Need help identifying this cylindrical layered rock found in Bolivia [closed]

I found this rock in a tropical climate river in Bolivia (specifically Ivirgarzama). It seems to have 5 or 6 layers. 1st layer is a slightly course matte rock layer 2nd layer is a more glossy rock ...
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2answers
944 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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1answer
97 views

What rock is this that I found on beach? [closed]

Found this on the beach in NY - it is a dark red colored rock with the green stones:
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67 views

What is in this rock? [closed]

There were many, many examples of this, my photo simply shows a situation where I had even light and time to take a photo without making anyone wait for me. The basic rock is obviously sandstone. ...
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0answers
5k views

What is this black, shiny, smooth, kind of heavy, metallic rock? [closed]

Its kind of heavy for it size, though not extreme - about two pounds. Looks like a chunk of metal, but not quite sure what it is.
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0answers
80 views

What is this 6in Nor Cal beach boulder with waxy veins? [closed]

Nor Cal beach @ low tide. 6in, photographed wet, post acid wash. Veins look waxy.
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0answers
310 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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0answers
133 views

Can you Identify this? [closed]

I went hiking and I found this rock with something inside. I would like to know what it is. Thanks!!!
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0answers
120 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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0answers
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
647 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 ...
2
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3answers
221 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 ...
2
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1answer
300 views

Help Identifying this rock with a rainbow [closed]

I found this rock and I want to know what it is. It looks like green-grey and when I put one side of the rock on the sun, it changes its colors on that side. Thanks
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2answers
438 views

Was there once a glacier over Starcke national park in Queensland Australia?

I was randomly exploring Google Earth when I came across some sort of rock formation in northern Australia. The location of the rock formation with respect to Australia is shown below. It is in or ...
2
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1answer
362 views

Please help me identify this very cool rock with a face [closed]

I found this rock where there was a lot of petrified wood but this does not resemble any of the many pieces of petrified wood that I have collected. It has the shape of a face, in my opinion. It has ...
2
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1answer
247 views

Unidentified black spherical rock [closed]

I need help in indentifying this rock.. The diameter of the rock is 18cm (Approx) and the weight is 9.876 kgs (21.772853 pounds). It feels much heavier in the hand than an ordinary earth rock.
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1answer
761 views

Could you please identify this rock for me [closed]

I found this rock several days ago and think it looks like RUBY ! Could you please help me to recognize it ?
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1answer
174 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
650 views

Rock ID: translucent, hard, smooth, heavy for size dark green/black to white(around edges) east coast Australia in surf [closed]

Hi there, I found this rock in the surf somewhere on the east coast of Australia around 20 years ago. Not sure if this is sea glass or a rock but hoping someone can help me identify as it has bugged ...
2
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1answer
182 views

Is this a rock or something else? [closed]

I found this on the bank of the Fraser River in BC, and at first I thought it was a piece of wood. But when I picked it up, I realized it wasn’t. Does anyone know what formed the rings? Is it even a ...