# Classes of Rock: What is Quartz?
**URL:** https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066
**Category:** Factual Questions
**Created:** [February 23, 2010, 2:11am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066 "2010-02-23T02:11:45Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [February 23, 2010, 2:11am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/1 "2010-02-23T02:11:45Z")
I assume quartz is formed under great pressure and at high temps. In short, what class of rock does this fall into (sedimentary, etc.)? Or, are such stones (including various semi-precious stones which are a variant of white quartz) in a class by themselves?
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### Author:  [@srzss05](https://boards.straightdope.com/u/srzss05)
#### Post date: [February 23, 2010, 2:14am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/2 "2010-02-23T02:14:03Z")
Quartz is a mineral, not a rock.
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### Author:  [@Caught\_Work](https://boards.straightdope.com/u/Caught_Work)
#### Post date: [February 23, 2010, 2:17am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/3 "2010-02-23T02:17:55Z")
Quartz is a mineral not a rock so as far as I understand it is neither igneous, metamorphic or sedimentary.
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### Author:  [@Isamu](https://boards.straightdope.com/u/Isamu)
#### Post date: [February 23, 2010, 2:38am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/4 "2010-02-23T02:38:02Z")
Yeah, as others said it’s a mineral. It’s also a _component_ of many types of rock.
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### Author:  [@Ludovic](https://boards.straightdope.com/u/Ludovic)
#### Post date: [February 23, 2010, 2:58am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/5 "2010-02-23T02:58:19Z")
Like the others said, it’s a mineral, and can be found in all three types: sedimentary (e.g. sandstone), igneous (e.g. granite), and metamorphic (e.g. metamorphosized granite such as some gneisses) rock.
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### Author:  [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)
#### Post date: [February 23, 2010, 3:01am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/6 "2010-02-23T03:01:00Z")
Assuming we’re now clear on rock vs. mineral, quartz is formed originally in igneous or hydrothermal environments (hydrothermal rocks don’t really fit into the igneous, sedimentary, metamorphic categories-- they’re rocks that precipitate out of water that is derived from and/or altered by magma bodies). Quartz is a very hardy mineral, and so it is also very commonly found in metamorphic and sedimentary rocks (most of the world’s sand is quartz), but this isn’t where it crystallized originally. Generally the big crystals you might find lying around are going to be from magma bodies which cooled very slowly (pegmatites) or are hydrothermal.
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### Author:  [@Malleus\_Incus\_Stapes](https://boards.straightdope.com/u/Malleus_Incus_Stapes)
#### Post date: [February 23, 2010, 7:33pm UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/7 "2010-02-23T19:33:13Z")
> [@GreasyJack](#):
>
> Assuming we’re now clear on rock vs. mineral
I’m not. Okay, so quartz isn’t a rock because it’s a crystal. So what’s the difference between a rock and a mineral?
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### Author:  [@srzss05](https://boards.straightdope.com/u/srzss05)
#### Post date: [February 23, 2010, 7:45pm UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/8 "2010-02-23T19:45:29Z")
> [@Malleus\_Incus\_Stapes](#):
>
> I’m not. Okay, so quartz isn’t a rock because it’s a crystal. So what’s the difference between a rock and a mineral?
Rocks are made up of minerals and mineraloids.
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### Author:  [@Quartz](https://boards.straightdope.com/u/Quartz)
#### Post date: [February 23, 2010, 8:00pm UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/9 "2010-02-23T20:00:11Z")
Actually, I prefer orchestral music. 😃
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### Author:  [@Duckster](https://boards.straightdope.com/u/Duckster)
#### Post date: [February 23, 2010, 8:29pm UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/10 "2010-02-23T20:29:11Z")
Just make sure no one in this thread gets upset. We don’t want anyone caught between a rock and a hard place. 🙂
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### Author:  [@LouisB](https://boards.straightdope.com/u/LouisB)
#### Post date: [February 23, 2010, 9:40pm UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/11 "2010-02-23T21:40:17Z")
Quartz is SiO2 (Silicon Dioxide) and is one of the most common minerals on Earth. It is impervious to all acids except sulfuric, IIRC, and is found in both right and left handed formation. It exists in two forms, alpha and beta quartz; alpha quartz is piezoelectric while beta quartz is not. If alpha quartz is heated to 573 degrees C, it transforms into beta quartz. It melts at ~ 1700 degrees C.
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### Author:  [@racer72](https://boards.straightdope.com/u/racer72)
#### Post date: [February 24, 2010, 1:29am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/12 "2010-02-24T01:29:39Z")
I prefer to buy my milk in quartz bottles.
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### Author:  [@dtilque](https://boards.straightdope.com/u/dtilque)
#### Post date: [February 24, 2010, 10:02am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/13 "2010-02-24T10:02:11Z")
> [@Duckster](#):
>
> Just make sure no one in this thread gets upset. We don’t want anyone caught between a rock and a hard place. 🙂
If everyone is gneiss, that won’t happen.
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### Author:  [@Isamu](https://boards.straightdope.com/u/Isamu)
#### Post date: [February 24, 2010, 11:01am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/14 "2010-02-24T11:01:21Z")
Geologists give me the schist.
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### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [February 26, 2010, 3:41am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/15 "2010-02-26T03:41:03Z")
These jokes are very shale-low!
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### Author:  [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)
#### Post date: [February 26, 2010, 4:00am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/16 "2010-02-26T04:00:52Z")
I suppose I should add at this point that sometimes quartz thinks so much of itself that it acts like it’s a rock. When this happens, it’s called vain quartz.
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### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [February 26, 2010, 4:04am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/17 "2010-02-26T04:04:31Z")
Quartz can be embarrassed quite easily. When it does, this is known as rose quartz!
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### Author:  [@Isamu](https://boards.straightdope.com/u/Isamu)
#### Post date: [February 26, 2010, 5:14am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/18 "2010-02-26T05:14:29Z")
> [@GreasyJack](#):
>
> I suppose I should add at this point that sometimes quartz thinks so much of itself that it acts like it’s a rock. When this happens, it’s called vain quartz.
Comedy gold!
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### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [February 26, 2010, 11:34am UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/19 "2010-02-26T11:34:39Z")
I should add I thought minerals of being things more like ores. So, what are ores classified as?
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### Author:  [@AWB](https://boards.straightdope.com/u/AWB)
#### Post date: [February 26, 2010, 1:09pm UTC](https://boards.straightdope.com/t/classes-of-rock-what-is-quartz/530066/20 "2010-02-26T13:09:55Z")
From Wikipedia:
> [@](#):
>
> Quartz is an essential constituent of granite and other felsic **igneous** rocks.
>
> It is very common in **sedimentary** rocks such as sandstone and shale and is also present in variable amounts as an accessory mineral in most carbonate rocks.
>
> It is also a common constituent of schist, gneiss, quartzite and other **metamorphic** rocks.
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