# How can I tell what rocks have cool stuff inside of them?
**URL:** https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704
**Category:** Factual Questions
**Created:** [April 11, 2007, 9:39pm UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704 "2007-04-11T21:39:11Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@\_kat\_herbrain](https://boards.straightdope.com/u/_kat_herbrain)
#### Post date: [April 11, 2007, 9:39pm UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/1 "2007-04-11T21:39:11Z")
When I was a kid, my grandparents had this rock in their house that looked normal on the outisde, but when you turned it around it was cut in half and ha=d beautiful quartz inside of it. Since then, I have been breaking rock only to be disappointed time and time again. How can I tell what rocks are quartz? :smack:
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### Author:  [@Hampshire](https://boards.straightdope.com/u/Hampshire)
#### Post date: [April 11, 2007, 9:43pm UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/2 "2007-04-11T21:43:30Z")
I think your looking for [geodes](http://en.wikipedia.org/wiki/Geode).
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### Author:  [@jjimm](https://boards.straightdope.com/u/jjimm)
#### Post date: [April 11, 2007, 9:44pm UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/3 "2007-04-11T21:44:19Z")
Hi **❤kat&&herbrain❤**. The rocks you’re referring to are called [geodes](http://en.wikipedia.org/wiki/Geode). They’re quite difficult to spot outdoors. According to [this site](http://www.earthsky.org/faq/49969/opening-geode):
> [@](#):
>
> It helps to know where to look—a geodiferous outcrop of rocks. With practice, you can learn to identify a geode—they’re usually round or egg-shaped, and the weathered ones look like cauliflower on the outside.
Hopefully a geologist will be along to give you better geode-spotting information. Happy hunting!
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### Author:  [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)
#### Post date: [April 12, 2007, 3:05am UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/4 "2007-04-12T03:05:52Z")
You should have no problem finding places to buy geodes online. Some places sell them already broken in half. Some sell them whole so you can break them open and see the crystals inside for the first time.
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### Author:  [@Squink](https://boards.straightdope.com/u/Squink)
#### Post date: [April 12, 2007, 3:18am UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/5 "2007-04-12T03:18:42Z")
There’s a series of books called [Roadside geology of (state or province)](http://www.google.com/search?q=%22roadside+geology+of%22&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a), that can help you find geodes and such. Also there are various books called “rock hunters guide to…” or “gem hunters guide to…” If your local library doesn’t have them, you can buy them online.
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### Author:  [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)
#### Post date: [April 12, 2007, 5:33am UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/6 "2007-04-12T05:33:09Z")
[QUOTE=Wendell Wagner]
You should have no problem finding places to buy geodes online. Some places sell them already broken in half. Some sell them whole so you can break them open and see the crystals inside for the first time.
[/QUOTE]
Most of the ones that sell them whole don’t guarantee that they’ll contain quartz. Maybe today with NDE (non destructive evaluation techniques), but the last time I looked (several years ago), they were “70% guaranteed”, or something like that.
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### Author:  [@JohnGalt](https://boards.straightdope.com/u/JohnGalt)
#### Post date: [April 12, 2007, 1:48pm UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/7 "2007-04-12T13:48:35Z")
Look for a show on the Travel Channel called “Best Places to Find…”; they have an episode on geodes, calling them thunder-eggs. Other episodes show where to find diamonds (Arkansas), glowing rocks, meteorites, and even old bottles from the pits of abandoned outhouses (I hope they were abandoned).
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### Author:  [@What\_Exit](https://boards.straightdope.com/u/What_Exit)
#### Post date: [April 12, 2007, 2:15pm UTC](https://boards.straightdope.com/t/how-can-i-tell-what-rocks-have-cool-stuff-inside-of-them/399704/8 "2007-04-12T14:15:25Z")
Prior Thread that might help:
[Best place to find uncut geodes?](http://208.100.26.199/sdmb/showthread.php?t=397224&highlight=Geodes)
I followed this advice:
[QUOTE=lee]
American Science and Surplus sells them. [http://www.sciplus.com/](http://www.sciplus.com/)
[/QUOTE]
I bought 20 Geodes for my kids and 18 contained crystal. We had a lot of fun breaking the Geodes, cleaning them up and shining lights and lasers in them.
Jim