Questions tagged [rocks]

Questions about rock types, formation, chemistry, and physics.

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1answer
102 views

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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62 views

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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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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1answer
37 views

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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1answer
46 views

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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2answers
39 views

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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1answer
62 views

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 ...
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1answer
74 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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1answer
41 views

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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4answers
90 views

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'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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4answers
8k views

Why is coal classified as a sedimentary rock?

Something just clicked in my head today. Rocks, by the definition I was taught, are composed of minerals which in turn are by definition not organic, so they are or were not alive. However. Coal, ...
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58 views

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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12 views

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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1answer
36 views

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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100 views

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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What is the oldest sediment?

Sedimentary rocks in Akilia or at Hudson Bay have been proposed as the oldest in the world. My question is not related to rocks, but rather to sediment while still forming sedimentary deposits but ...
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0answers
25 views

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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2answers
112 views

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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1answer
216 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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3answers
125 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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53 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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4answers
18k views

What was the first rock in the rock cycle?

I am an undergraduate student but I am a tutor at a High School, and one student asked me. Attempting to explain the rock cycle "if one rock turns into the other then which came first" my gut is ...
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48 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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2answers
574 views

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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1answer
43 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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4answers
85 views

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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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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1answer
309 views

Spatial Continuity in python

I have data like this of rocks from 3 blast holes: These are the rock properties of each blast hole of a mining site. The rock properties come from the Block model of that mining site. I want to ...
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1answer
81 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 ...
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26 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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1answer
66 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 ...
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2answers
184 views

Why are metals so separated in the Earths crust? [duplicate]

I find it very surprising that metal ore deposits are so separate, and unevenly separated on the Earth. I do understand that there were various different conditions at some point in time in the ...
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1answer
619 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 ...
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644 views

What is the global distribution of oil filled geodes?

In a general 40 mile radius of Keokuk, Iowa many sedimentary geodes can be found. They are abundant in the Warsaw Formation with the type section at Geode Glenn in Warsaw, Illinois. In one specific ...
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3answers
409 views

Is there a widely accepted reason for the formation of tafoni?

Expansion of tafoni seems to be based on weathering (seems reasonable enough.) But what creates them in the first place? There are a number of explanations online (Wikipedia lists eight plausible ...
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2answers
85 views

Curious natural patterns on the surface of basalt blocks that make up the sidewalk

During one of my walks through the city streets, I noticed that some basalt blocks that make up the sidewalk have in their surface some very curious natural patterns: The photos above was taken at ...
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2answers
21k 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 ...
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2answers
62k views

Are the processes of the rock cycle currently in dynamic equilibrium?

The standard representation of the rock cycle usually looks like this: Does each stage of the rock cycle currently balance? That is, are the various processes in dynamic equilibrium, so that 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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0answers
182 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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4answers
1k views

How is this crumbly crystal-rich rock formed?

I found this crumbly rock embedded in the channel walls of a small creek in Everett, WA, USA. (North Creek that flows through McCollum Park.) If possible, I'd like to know how the rock formed... what ...
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1answer
276 views
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561 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
37 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
507 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
235 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
971 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 ...
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1answer
137 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 ...
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1answer
211 views

Identification of limestone type

These are images of a stone found and used extensively in the Jammu & Kashmir region between India and Pakistan. These are called devir or devri in the local parlance. Following is the ...