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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11
votes
3answers
1k views

Identifying sedimentary rocks in hand specimen

I'm currently learning how to identify rocks in hand specimen. The initial classification into igneous, metamorphic, and sedimentary is mostly ok, but I'm having a problem with further identifying ...
1
vote
1answer
71 views

What type of mineral is this? [closed]

My grandfather found this thing.
11
votes
2answers
4k views

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 ...
3
votes
1answer
690 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) ...
4
votes
1answer
185 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....
2
votes
3answers
231 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 ...
7
votes
2answers
184 views

Recreating the rock cycle

I want to recreate the rock cycle using some item that can behave as a rock. The purpose of this is to get a point across to my students about how really there is a reason why the rock cycle is called ...
6
votes
1answer
1k views

How to identify a predator's coprolite from an herbivore's?

I have a coprolite that is 8" by 5" and weighs 8 lbs. The shape is similar to a lumpy brain, the colors below outer crust are deep red and the crust is pastel green and grey. It has a strong density ...
4
votes
1answer
1k 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 ...
5
votes
1answer
237 views

What could have formed the pattern inside this piece of siltstone?

I have what i think is a piece of siltstone with an interesting pattern on the face. It looks like a lichen or lightning bolt, as shown in the picture. The interior of the pattern is the same color as ...
3
votes
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 ...
14
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1answer
230 views

How are the patterns in solid rock born

I took this photo on my vacation in Finland showing white stripes in the rock going different ways. How are these patterns born?
13
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1answer
529 views

Formation of limestone without living organisms?

Limestones are formed mostly from skeletal fragments of marine organisms. However, calcium carbonate dissolves naturally in water, so the living organisms are not the only source of it in water. Is ...

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