<p><a href="https://en.wikipedia.org/wiki/Syenite" rel="nofollow noreferrer">Syenite</a> is a granite like igneous rock that is deficient in quartz. If it contains quartz the amount of quartz is less than 5 percent.</p>
<p><a href="https://geology.com/rocks/conglomerate.shtml" rel="nofollow noreferrer">Conglomerate</a> is sedimentary rock that contains clasts (rock fragments - the sedimentary component) that have were once washed down a river and are held together by  quartz or calcite. The rock fragments (clasts) with the matrix of the conglomerate are <strong>rounded</strong>, which indicates they tumbled down a river.</p>
<p>The clasts within the conglomerate can be from a variety of different rock types, including: quartz or feldspar, quartzite, sandstone, limestone, granite, basalt, and gneiss. It is possible that syenite can be a component of a conglomerate, it depends on the local geology.</p>
<p>Regarding the floater, with only one sample for an area it is difficult to tell, but is seems unlikely to indicate a local outcrop. As you indicate it may have been deposited there during road construction works.</p>

CC BY-SA 4.0
2023-06-14T21:45:04.200Z
2023-06-14T21:45:04.200Z
Fred
<p>Near an old fire trail, I found a single fist-size igneous rock that I identified (as an amateur geologist) as belonging to a formation that is not known of in the area but is known to occur in the neighbouring district, although not common there. Naturally, I was interested in finding out if there was an outcrop and looked for more float samples, but twenty minutes of searching yielded no more samples. My question is, how reliable are float samples? Is there probably an outcrop? Or, assuming my ID was correct, could I just have been that the bulldozer that cut the road all those years ago came directly from the small part of the neighbouring district where these rocks are found? Or did the bulldozer move it from elsewhere on the hill, but there still probably is an outcrop in the immediate vicinity?</p>
<p>Apologies for the rather specific (and long-winded) question; this Stack Exchange is looking for more general questions. However, I would like to add if an intrusive igneous rock such as syenite could be shed from a quartz conglomerate. It seems unlikely, but that is the primary formation above the spot where it was found and could explain its occurrence. (Should I have created a separate question for this?)</p>

CC BY-SA 4.0
2023-06-14T10:39:20.483Z
Suggest you take the last part of the question and make it a separate question indeed, as it seems separate in general
JeopardyTempest
<rocks>
How accurate are float samples when looking for outcrops?
Tom P
# How accurate are float samples when looking for outcrops?

(Asked by: username_0 on 2023-06-14)

Near an old fire trail, I found a single fist-size igneous rock that I identified (as an amateur geologist) as belonging to a formation that is not known of in the area but is known to occur in the neighbouring district, although not common there. Naturally, I was interested in finding out if there was an outcrop and looked for more float samples, but twenty minutes of searching yielded no more samples. My question is, how reliable are float samples? Is there probably an outcrop? Or, assuming my ID was correct, could I just have been that the bulldozer that cut the road all those years ago came directly from the small part of the neighbouring district where these rocks are found? Or did the bulldozer move it from elsewhere on the hill, but there still probably is an outcrop in the immediate vicinity?

Apologies for the rather specific (and long-winded) question; this Stack Exchange is looking for more general questions. However, I would like to add if an intrusive igneous rock such as syenite could be shed from a quartz conglomerate. It seems unlikely, but that is the primary formation above the spot where it was found and could explain its occurrence. (Should I have created a separate question for this?)

**Tags:** rocks

> **Comments:**
> **username_1**: Suggest you take the last part of the question and make it a separate question indeed, as it seems separate in general  

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## 1 answers

### Answer by username_2 on 2023-06-14. Score: 3 | Accepted answer

[Syenite](https://en.wikipedia.org/wiki/Syenite) is a granite like igneous rock that is deficient in quartz. If it contains quartz the amount of quartz is less than 5 percent.

[Conglomerate](https://geology.com/rocks/conglomerate.shtml) is sedimentary rock that contains clasts (rock fragments - the sedimentary component) that have were once washed down a river and are held together by quartz or calcite. The rock fragments (clasts) with the matrix of the conglomerate are **rounded**, which indicates they tumbled down a river.

The clasts within the conglomerate can be from a variety of different rock types, including: quartz or feldspar, quartzite, sandstone, limestone, granite, basalt, and gneiss. It is possible that syenite can be a component of a conglomerate, it depends on the local geology.

Regarding the floater, with only one sample for an area it is difficult to tell, but is seems unlikely to indicate a local outcrop. As you indicate it may have been deposited there during road construction works.


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