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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3
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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 ...
5
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1answer
104 views

There are cloud identification guides, are there also (guided) rock identification websites?

Seeing all these rock identification questions, got me wondering, is there no straightforward guided rock identification website? In Intro to Geology lab, I remember going through a bit of a process ...
3
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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!!!
1
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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 ...
2
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1answer
242 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.
0
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3answers
893 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, ...
4
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1answer
711 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 ...
3
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2answers
912 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.
6
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1answer
660 views

What are the blue spots in this rock? [closed]

The rock is 4 inches (~10 cm) long. The vendor claims this rock is from K2. Are the blue spots real or painted on?
3
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1answer
95 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:
6
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2answers
2k views

Why are most minerals so rare?

There are 4,660 known minerals, so why are most of them so rare? Is it to do with the structure of minerals?
2
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1answer
742 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 ?
10
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1answer
476 views

Are “monoliths” giant, isolated rocks sitting in dirt, or are they continuous with bedrock

I am at a loss for the precise, correct terminology, but I have read in Wikipedia that Uluru is not a monolith, but Savandurga is, and that I probably shouldn't be using the word monolith to begin ...
5
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1answer
333 views

What are the circular features in this rock? [closed]

I found this rock by the shore of Lake Ontario. It's light weight and it was grouped with some other rocks with the same patterns.
2
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1answer
355 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 ...
5
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1answer
383 views

I'm trying to find the name of this rock [closed]

I found it upstate New York... Can someone please help me identify this rock. I added photos with different lighting. It's a very dark purple with a mix color showing more in the center. Its very soft ...
8
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1answer
906 views

Rock ID: brittle black/white w/ crystals & mica-like cleavage layers, Raleigh, NC, USA [closed]

Where it was Found: I found the rock laying on the sidewalk near some landscaping at my apartment complex in Raleigh, NC. Size: The largest intact portion of the rock is about 2.2 cm in diameter. ...
4
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1answer
424 views

What rock is this? [closed]

I've had this little guy for a while now and have been trying to identify it for some time with no luck. It looks like its oxidized with tiny little crystals, but it's hard to tell for sure. Any ...
10
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2answers
16k views

How long does it take for a stone to alter?

We see stones and they appear to be the same throughout our life time. Mountains also appear to not significantly change. So do mountains and stones decompose? What is the life span of a stone? After ...
4
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2answers
191 views

Help me to identify this rock, please, [closed]

Can anyone tell me what this rock is? It was found on the rocky beach at 'Glen Boreraig' on the Isle of Skye, Scottland. Definitely water-worn. It is 9.5 cm x 4.5 cm with inner darker part 4.5 cm x ...
1
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2answers
730 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 ...
3
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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 ...
4
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1answer
402 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?
2
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2answers
426 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
81 views

Color in Gems and Rocks [duplicate]

Why is it that gems/ rocks, such as Ruby, Sapphire, Topaz, etc... all have their own unique colors? Is this something that happens from chemical attraction with each stone upon formation?
4
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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
votes
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 ...
0
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1answer
585 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 ...
0
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1answer
159 views

Rock ID: Bone and potato-shaped, copper-colored [closed]

I found these two intriguing rocks on the UK's seaside. They have an unusual potato shape and copper/green color. Whrn knocked against each other, the sound is clear, metallic and the vibrations keep ...
7
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3answers
2k views

How was this egg shaped rock made and what is it? [closed]

The following small egg-like rock was found laying on the ground in Tampere, a city in southern Finland. It weights about 950 grams, has a volume of about 360 cm3 and thus a density of about 2600 kg/...
1
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0answers
132 views

Can you help me identify this rock? [closed]

We found this in our back yard (in Michigan) while digging one day. I'm curious about it, it seems different than others we've found. It's a pretty good size, about the size of a basketball.
3
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0answers
117 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
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 ...
2
votes
1answer
173 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 ...
0
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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 ...
4
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2answers
866 views

How this sedimentary rock is made?

Apologies in advance for a beginners question. Different rock types make me curious and recently went to an area where interesting sedimentary rock is all over. As the area is on the coast, sea has ...
0
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1answer
44 views

Is there any covalent crystals that can be easily synthesized?

I am looking for a kind of crystal that can be artificially made at relatively low temperatures (below 1500 degree Celsius) and relatively quickly (not geological time). The product is ideally ...
1
vote
1answer
248 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 ...
6
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0answers
164 views

Basalt vs. columnar basalt

I recently visited a cliff on the south coast of Ulva in the Inner Hebrides where there are ~10m thick flows of columnar basalt. The columnar basalt forming most of the cliff is sandwiched between ...
3
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0answers
48 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 ...
2
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0answers
628 views

What type of rock is this powdery white rock with a fairly smooth dark shell and rusty patches I found while digging up pipe? [closed]

This rock is sort of a dark grey/black and kind of shiny but more matte I'd say. It does have some brown rust-like spots on it. And the inside has little dimples in a what seems to be more chalky ...
5
votes
1answer
125 views

Strange coating in old lime mine shaft

Near Prague,Czech Republic is old lime mine. Most of it is closed but one short transport tunnel under one hill is publicly accessible. Tunnel has profile around 2,5x2,5m and it's slightly bended and ...
1
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0answers
390 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 ...
9
votes
3answers
645 views

What do you call boulders of non sedimentary rock that were lithified into sandstone?

I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes ...
1
vote
1answer
71 views

What type of mineral is this? [closed]

My grandfather found this thing.
2
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1answer
80 views

Unknown semi-precious stone [closed]

On the handwork market I've found piece like this Merchant (who was reseller) didn't know its name. Have you any idea what is that? EDIT: I think it was about 5 on Moch's scale. It was black with ...
7
votes
2answers
2k views

Rock ID: Geode, soft, dull black exterior with crystal inside, from Snæfellsnes, Iceland [closed]

My fiancée found this on a recent trip to Iceland, on Snæfellsnes peninsula - she spotted the sparkle of the crystals among the abundant black, grey, and dark red rocks. There is a roadside vista spot ...
4
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0answers
564 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 ...
4
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2answers
823 views

Can you confirm if this rock is sandstone - it is this from Cape Cod, MA, USA [closed]

A few years ago I found this unusual looking rock while walking around the beach of Cape Code, MA, USA. My guess is that it is sandstone, but I didn't see any others like it on my stay. It is has ...
3
votes
1answer
576 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) ...