<p>This is a really bad question, because all three can lack fossils, or all three can have fossils. The definition of "minerals" is also a bit unclear, because fossils are also made out of minerals. I'll assume that by minerals they mean non-biogenic minerals. Let's go through each one of them:</p>

<blockquote>
  <p>a clastic sedimentary rock</p>
</blockquote>

<p>This rock will have minerals, because this is what is being transported. Usually quartz, feldspars, clays, heavy minerals, etc. But, it can also have fossils. Fossils can be transported as well, and it is not uncommon to find fossils in clastic sedimentary rocks. They are usually not intact, but still fossils nonetheless.</p>

<blockquote>
  <p>a chemical sedimentary rock</p>
</blockquote>

<p>This will have minerals, obviously. This might also have fossils: what if there were organisms around while the chemical rock formed? Could be fossils falling from above into a carbonate precipitate, or insects in an evaporite basin. However, this is probably the least likely rock to contain fossils. If you have to choose only one, this would be it (unfortunately).</p>

<blockquote>
  <p>iii) a biochemical sedimentary rock</p>
</blockquote>

<p>This sounds like an obvious one to contain fossils, but it may not be. What about limestones where all of the fossils were broken down to unrecognizable fragments of calcite? Also known as a micrite? This would be biogenic, but it wouldn't be clear what fossils are there.</p>

CC BY-SA 3.0
2017-05-02T23:40:35.597Z
Sir, your explanation is just awesome. I think I agree with you now that the question was a bad one. I really benefited a lot from you!
Asmaa
CC BY-SA 3.0
2017-05-02T23:23:36.110Z
2017-05-02T23:23:36.110Z
Gimelist
<p>In my text book I came across this multiple-choice question</p>
<blockquote>
<p>A sedimentary rock consists of only minerals and lacks fossils, it could be classified as:</p>
<p>i) a clastic sedimentary rock</p>
<p>ii) a chemical sedimentary rock</p>
<p>iii) a biochemical sedimentary rock</p>
</blockquote>
<p>Of course I would exclude &quot;a biochemical&quot;, but I am confused between <em>clastic</em> and <em>chemical</em>. I did some research on google but didn't find a precise answer. However, I found that both of them could contain only minerals.
So, I hope someone could help me here!</p>

CC BY-SA 3.0
2017-05-02T21:30:19.433Z
Everything is made of minerals. I assume what it means is that it lacks lithic fragments or bioclasts. I can still think of examples of all three types that fit these criteria though so not a it's not really a very good question.
bon
CC BY-SA 3.0
2017-05-02T21:53:14.583Z
@bon, OK, but if you had this question in an exam which of the choices you would choose?
Asmaa
CC BY-SA 3.0
2017-05-02T21:56:15.913Z
Why do I only have to pick one? I would give examples of all three.
bon
CC BY-SA 3.0
2017-05-02T22:54:58.730Z
Second that, all three would be the only correct answer if I had to correct that exam.
user2821
<geology><mineralogy><sedimentology><homework><fossils>
A sedimentary rock with only minerals
Asmaa
# A sedimentary rock with only minerals

(Asked by: username_0 on 2017-05-02)

In my text book I came across this multiple-choice question

> A sedimentary rock consists of only minerals and lacks fossils, it could be classified as:
>
> i) a clastic sedimentary rock
>
> ii) a chemical sedimentary rock
>
> iii) a biochemical sedimentary rock

Of course I would exclude "a biochemical", but I am confused between *clastic* and *chemical*. I did some research on google but didn't find a precise answer. However, I found that both of them could contain only minerals.
So, I hope someone could help me here!

**Tags:** geology, mineralogy, sedimentology, homework, fossils

> **Comments:**
> **username_1**: Everything is made of minerals. I assume what it means is that it lacks lithic fragments or bioclasts. I can still think of examples of all three types that fit these criteria though so not a it's not really a very good question.  
> **username_0**: @username_1, OK, but if you had this question in an exam which of the choices you would choose?  
> **username_1**: Why do I only have to pick one? I would give examples of all three.  
> **username_2**: Second that, all three would be the only correct answer if I had to correct that exam.  

---

## 1 answers

### Answer by username_3 on 2017-05-02. Score: 5 | Accepted answer

This is a really bad question, because all three can lack fossils, or all three can have fossils. The definition of "minerals" is also a bit unclear, because fossils are also made out of minerals. I'll assume that by minerals they mean non-biogenic minerals. Let's go through each one of them:

> a clastic sedimentary rock

This rock will have minerals, because this is what is being transported. Usually quartz, feldspars, clays, heavy minerals, etc. But, it can also have fossils. Fossils can be transported as well, and it is not uncommon to find fossils in clastic sedimentary rocks. They are usually not intact, but still fossils nonetheless.

> a chemical sedimentary rock

This will have minerals, obviously. This might also have fossils: what if there were organisms around while the chemical rock formed? Could be fossils falling from above into a carbonate precipitate, or insects in an evaporite basin. However, this is probably the least likely rock to contain fossils. If you have to choose only one, this would be it (unfortunately).

> iii) a biochemical sedimentary rock

This sounds like an obvious one to contain fossils, but it may not be. What about limestones where all of the fossils were broken down to unrecognizable fragments of calcite? Also known as a micrite? This would be biogenic, but it wouldn't be clear what fossils are there.

> **Comments:**
> **username_0**: Sir, your explanation is just awesome. I think I agree with you now that the question was a bad one. I really benefited a lot from you!  

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