<p>Black elongated crystals are mostly hornblendes. The rock itself is (probably) horblende andersite or hornblende dacite. Both are intermediate volcanic rocks.</p>

CC BY-SA 3.0
2017-09-26T17:09:18.170Z
2017-09-26T17:09:18.170Z
Gabija
<p>I found this rock near my home in the high desert of south central Utah (near Capitol Reef National Park). The sides are symmetrical and smooth -- shaped somewhat like a canoe. It is 6 1/2" long; 1 1/2" at widest point. The top is sheared off and sparkles in the light. It is embedded with flakes of a shiny, black glasslike material, possibly obsidian. The Fremont culture occupied the area and left an abundance of tools, points, and chip rock, many of which were sourced from elsewhere; most likely the result of trading. A neighbor and I came up with an uninformed theory. Would appreciate any informed observations.
<a href="https://i.sstatic.net/nMjTA.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/nMjTA.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2017-09-21T17:48:50.350Z
Do you have more photo's, preferably out of direct sunlight? This one is oversaturated. And any more information [mentioned here](http://meta.earthscience.stackexchange.com/questions/124/a-guide-for-asking-identify-this-rock-questions)?
Jan Doggen
CC BY-SA 3.0
2017-09-22T10:32:25.580Z
I don't think the black stuff is obsidian. It definitely looks like crystals, possibly phenocrysts of amphibole or pyroxene.
Gimelist
CC BY-SA 3.0
2017-09-25T04:05:56.080Z
the shape could be due to wind based weathering, it often produces smooth sided angular ventifacts. https://www.researchgate.net/figure/284360115_fig1_Figure-1-A-the-three-mature-shapes-of-small-ventifacts-predicted-by-the-model-described
John
<geology>
What is this canoe-shaped rock with obsidian? flakes?
DesertJon
# What is this canoe-shaped rock with obsidian? flakes?

(Asked by: username_0 on 2017-09-21)

I found this rock near my home in the high desert of south central Utah (near Capitol Reef National Park). The sides are symmetrical and smooth -- shaped somewhat like a canoe. It is 6 1/2" long; 1 1/2" at widest point. The top is sheared off and sparkles in the light. It is embedded with flakes of a shiny, black glasslike material, possibly obsidian. The Fremont culture occupied the area and left an abundance of tools, points, and chip rock, many of which were sourced from elsewhere; most likely the result of trading. A neighbor and I came up with an uninformed theory. Would appreciate any informed observations.
[![enter image description here](https://i.sstatic.net/nMjTA.jpg)](https://i.sstatic.net/nMjTA.jpg)

**Tags:** geology

> **Comments:**
> **username_1**: Do you have more photo's, preferably out of direct sunlight? This one is oversaturated. And any more information [mentioned here](http://meta.earthscience.stackexchange.com/questions/124/a-guide-for-asking-identify-this-rock-questions)?  
> **username_2**: I don't think the black stuff is obsidian. It definitely looks like crystals, possibly phenocrysts of amphibole or pyroxene.  
> **username_3**: the shape could be due to wind based weathering, it often produces smooth sided angular ventifacts. https://www.researchgate.net/figure/284360115_fig1_Figure-1-A-the-three-mature-shapes-of-small-ventifacts-predicted-by-the-model-described  

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## 1 answers

### Answer by username_4 on 2017-09-26. Score: 4

Black elongated crystals are mostly hornblendes. The rock itself is (probably) horblende andersite or hornblende dacite. Both are intermediate volcanic rocks.


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