<p>Nodules, as in chert nodules are common in limestone, but not confined to any particular sedimentary rock.</p>

CC BY-SA 3.0
2016-03-03T17:31:10.103Z
2016-03-03T17:31:10.103Z
Mickmick
<p>I believe the term you are looking for is &quot;Intraclast&quot;. That is, an allochthonous clast (one not formed in situ) that is not a single grain or mineral, but a rock composed of multiple other grains or minerals. An example would be a granule of siltstone lithified into a coarse sandstone or a granule of granite similarly lithified in a sandstone. To borrow the conglomerate example from above, a pebble or cobble of quartzite, or sandstone, or any rock included in that conglomerate is an intraclast. The quartz grains or clay or mica in that same conglomerate are all just clasts. These are chunks of other rocks (not individual minerals) included in a new sedimentary deposit.</p>

CC BY-SA 4.0
2024-05-10T23:41:00.383Z
2024-05-10T23:41:00.383Z
Josiah
<p>The word <a href="https://en.wikipedia.org/wiki/Xenolith" rel="nofollow">xenolith</a> (from ancient Greek, meaning stranger stone or foreign rock) is used to describe stones entrapped with an igneous matrix. However, as the reference states, </p>

<blockquote>
  <p>a broad definition could include rock fragments which have become encased in sedimentary rock</p>
</blockquote>

CC BY-SA 3.0
2016-02-29T03:32:21.667Z
As xenolith is a technical term in igneous petrology it's best to avoid its use in other areas to steer clear of confusion. I answered this as well, but wanted to comment on your answer. Technically correct is the best kind of correct!
Ben MS
CC BY-SA 3.0
2016-08-10T01:11:35.800Z
In this context I don't like the use of either 'xenolith' or 'erratic', both of which have highly specific connotations in igneous and glacial contexts, respectively. There isn't a specific term for the boulders you refer to, so resort to the time-honoured geologist's tradition of coining a new term. How about 'Terogoclast'? = large chunk of eroded / weathered rock.
Gordon Stanger
CC BY-SA 3.0
2016-02-28T07:47:38.090Z
2016-02-28T07:47:38.090Z
Fred
<p>The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a <strong>conglomerate</strong>. The fine-grained interstitial part is called the <strong>matrix</strong>, and the large pieces suspended in it are called <strong>clasts</strong>. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.</p>

<p>It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.</p>

CC BY-SA 3.0
2016-02-29T13:28:26.813Z
Then what do you refer to the stones as after they've been freed from the sandstone? There are large stones out there just laying in the sand like eratics, but they are there because they eroded out of the hoodoo.
ShemSeger
CC BY-SA 3.0
2016-02-29T21:29:14.847Z
@ShemSeger I'm not a sure there is a term for "rocks that used to be lithoclasts but are now just boulders sitting there". If there is, it's mostly likely an obscure term that no one knows unless you're an extremely old professor that insists on using excess jargon.
Gimelist
CC BY-SA 3.0
2016-02-29T22:38:03.910Z
If they're loose stones that have been eroded out and mobilised from being in a conglomerate, then they are referred to as whatever the relevant grain size is, from here: https://en.wikipedia.org/wiki/Grain_size The ones that you're talking about would just be boulders.
Ben MS
CC BY-SA 3.0
2016-03-01T09:16:34.283Z
I agree, it's just a clast. But I see the point of naming it something else after it's been released from the matrix material. In this case, the original sandstone acts like a carrier which then releases the boulders after. It reminds me of a glacial boulder which is sometimes called a ["glacial erratic"](https://en.wikipedia.org/wiki/Glacial_erratic).
Antonio
CC BY-SA 3.0
2016-03-02T04:23:00.867Z
@Antonio I'm very familiar with erratics. Actually, the Big Rock in Okotoks, Alberta pictured on that wikipedia article isn't far from here, only about a 2hrs drive. There's another one 40 minutes away, called the Glenwood erratic, both are popular for bouldering, I've climbed on both.  I vote for calling the released clast an, "emancipated clast."
ShemSeger
CC BY-SA 4.0
2024-05-10T23:43:27.580Z
Those clasts, if they are rocks and not individual mineral grains, are most correctly referred to as "intraclasts".
Josiah
CC BY-SA 3.0
2016-02-29T03:30:57.347Z
2016-02-29T03:30:57.347Z
Ben MS
<p>I'm convinced there is a word for this. I was in the <a href="http://www.albertaparks.ca/writing-on-stone/information-facilities/trails/hoodoo.aspx" rel="nofollow noreferrer">Hoodoos at Writing on Stone</a> this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos. </p>

<p>When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. </p>

<p><a href="https://i.sstatic.net/LAi9s.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/LAi9s.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2016-02-28T06:06:25.167Z
I love the idea of "non-sedentary rock". Is this one of Pratchett's trolls? (not editing in case it is actually a geological term and not a typo, but if a geologist comes along, check the title...)
Semidiurnal Simon
CC BY-SA 3.0
2016-02-28T07:53:14.183Z
@SimonW it actually fits :)
Gimelist
CC BY-SA 3.0
2016-03-02T04:25:45.837Z
@SimonW Auto correct is the bane of my existence...
ShemSeger
<geology><rocks><sedimentology><geomorphology><terminology>
What do you call boulders of non sedimentary rock that were lithified into sandstone?
ShemSeger
# What do you call boulders of non sedimentary rock that were lithified into sandstone?

(Asked by: username_0 on 2016-02-28)

I'm convinced there is a word for this. I was in the [Hoodoos at Writing on Stone](http://www.albertaparks.ca/writing-on-stone/information-facilities/trails/hoodoo.aspx) this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.

When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away.

[![enter image description here](https://i.sstatic.net/LAi9s.jpg)](https://i.sstatic.net/LAi9s.jpg)

**Tags:** geology, rocks, sedimentology, geomorphology, terminology

> **Comments:**
> **username_1**: I love the idea of "non-sedentary rock". Is this one of Pratchett's trolls? (not editing in case it is actually a geological term and not a typo, but if a geologist comes along, check the title...)  
> **username_2**: @SimonW it actually fits :)  
> **username_0**: @SimonW Auto correct is the bane of my existence...  

---

## 4 answers

### Answer by username_6 on 2016-02-29. Score: 8 | Accepted answer

The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a **conglomerate**. The fine-grained interstitial part is called the **matrix**, and the large pieces suspended in it are called **clasts**. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.

It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.

> **Comments:**
> **username_0**: Then what do you refer to the stones as after they've been freed from the sandstone? There are large stones out there just laying in the sand like eratics, but they are there because they eroded out of the hoodoo.  
> **username_2**: @username_0 I'm not a sure there is a term for "rocks that used to be lithoclasts but are now just boulders sitting there". If there is, it's mostly likely an obscure term that no one knows unless you're an extremely old professor that insists on using excess jargon.  
> **username_6**: If they're loose stones that have been eroded out and mobilised from being in a conglomerate, then they are referred to as whatever the relevant grain size is, from here: https://en.wikipedia.org/wiki/Grain_size The ones that you're talking about would just be boulders.  
> **username_8**: I agree, it's just a clast. But I see the point of naming it something else after it's been released from the matrix material. In this case, the original sandstone acts like a carrier which then releases the boulders after. It reminds me of a glacial boulder which is sometimes called a ["glacial erratic"](https://en.wikipedia.org/wiki/Glacial_erratic).  
> **username_0**: @username_8 I'm very familiar with erratics. Actually, the Big Rock in Okotoks, Alberta pictured on that wikipedia article isn't far from here, only about a 2hrs drive. There's another one 40 minutes away, called the Glenwood erratic, both are popular for bouldering, I've climbed on both.  I vote for calling the released clast an, "emancipated clast."  
> **username_4**: Those clasts, if they are rocks and not individual mineral grains, are most correctly referred to as "intraclasts".  

---

### Answer by username_3 on 2016-03-03. Score: 3

Nodules, as in chert nodules are common in limestone, but not confined to any particular sedimentary rock.


---

### Answer by username_4 on 2024-05-10. Score: 1

I believe the term you are looking for is "Intraclast". That is, an allochthonous clast (one not formed in situ) that is not a single grain or mineral, but a rock composed of multiple other grains or minerals. An example would be a granule of siltstone lithified into a coarse sandstone or a granule of granite similarly lithified in a sandstone. To borrow the conglomerate example from above, a pebble or cobble of quartzite, or sandstone, or any rock included in that conglomerate is an intraclast. The quartz grains or clay or mica in that same conglomerate are all just clasts. These are chunks of other rocks (not individual minerals) included in a new sedimentary deposit.


---

### Answer by username_5 on 2016-02-28. Score: 1

The word [xenolith](https://en.wikipedia.org/wiki/Xenolith) (from ancient Greek, meaning stranger stone or foreign rock) is used to describe stones entrapped with an igneous matrix. However, as the reference states,

> a broad definition could include rock fragments which have become encased in sedimentary rock

> **Comments:**
> **username_6**: As xenolith is a technical term in igneous petrology it's best to avoid its use in other areas to steer clear of confusion. I answered this as well, but wanted to comment on your answer. Technically correct is the best kind of correct!  
> **username_7**: In this context I don't like the use of either 'xenolith' or 'erratic', both of which have highly specific connotations in igneous and glacial contexts, respectively. There isn't a specific term for the boulders you refer to, so resort to the time-honoured geologist's tradition of coining a new term. How about 'Terogoclast'? = large chunk of eroded / weathered rock.  

---

