What Are Rattling Rocks and How Are They Formed?

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In summary, the conversation discusses a rock found in Eastern Oregon with a hollow interior and objects inside that rattle. The owner suspects it may be a geode, but the description does not match typical geodes. Suggestions are given for how to identify the rock, including taking it to a university geology department or cutting it open. It is also mentioned that similar rocks can be found in New Zealand and that they are likely of volcanic origin. The owner ultimately decides to keep the rock whole due to its rarity.
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Bryon Palmer
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I have a rock that I found while on a college class outing in Eastern Oregon. It is hollow inside and has multiple objects inside that rattle. I was told by a professor that isn't was formed when lava was ejected into the air and as it fell, it sort of ballooned out and solidified with smaller rocks inside of it. I have searched the internet and not found anything that fits this description. My guess is that it is a geode but it doesn't seem to match any of the descriptions or photos I have found. Can anyone tell me what it is?
 

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  • #3
Greg Bernhardt said:
Are you going to crack it open? :)
I would rather not.
 
  • #4
Seriously, online, looking at a picture, do you expect us to say what's inside? I have a rock that looks like marble on the outside, I've posted pictures, but the "marble" is striated across something visible inside, there are openings between the strings of "marble" like streaks. You can see another object encased inside of this marble like rock. Never seen anything like it, neither has anyone else. I love cool things like this.

If you do decide to open it let us know. You might want to take it to a University's geology department and see if they have any way of looking inside of it, even if to bore a small hole and insert a camera.
 
  • #5
Looks like it could be pumicite - if it floats in water it probably is.
 
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jim mcnamara said:
Looks like it could be pumicite - if it floats in water it probably is.
Thanks for the replies. No, it doesn't float. I didn't expect anyone to know, I was just hoping. Does the explanation given by my professor sound reasonable? We found 7 or 8 of them on our trip.
 
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Hi you Bryon
welcome to PF :smile:
Bryon Palmer said:
Thanks for the replies. No, it doesn't float. I didn't expect anyone to know, I was just hoping. Does the explanation given by my professor sound reasonable? We found 7 or 8 of them on our trip.

"rattle stones" ... have had lots of fun hunting for and finding the occasional ones of them when I lived in New Zealand ... there is also a sedimentary variety
your profs' explanation is quite reasonable

Bryon Palmer said:
My guess is that it is a geode but it doesn't seem to match any of the descriptions or photos

no, not really geodes, ( in the strictest definition) they form by a different mechanism ... in a mineral rich rock and water environment
and they are usually quite spherical inside and out

Basalt will often have cavities ... irregular in shape and filled with crystals of minerals such as Heulandite, Natrolite and a few other types of zeolitesDave
 
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davenn said:
Hi you Bryon
welcome to PF :smile:

"rattle stones" ... have had lots of fun hunting for and finding the occasional ones of them when I lived in New Zealand ... there is also a sedimentary variety
your profs' explanation is quite reasonable
no, not really geodes, ( in the strictest definition) they form by a different mechanism ... in a mineral rich rock and water environment
and they are usually quite spherical inside and out

Basalt will often have cavities ... irregular in shape and filled with crystals of minerals such as Heulandite, Natrolite and a few other types of zeolitesDave
Awesome! Thanks for the info Dave!
 
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  • #9
Sounds like a hollow version of our state rock: Thunderegg

Of course, without opening it, you'll never know.
 
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  • #10
There are a few geodes in eastern Oregon, Idaho and Utah that rattle. It's possible that there are stones inside yours, but some rattlers that have been cut open also have poorly formed quartz crystals that possibly broke off.
Smaller geodes tend to be spheroidal and are more typically picked up because they are small. We found several long, bomb-shaped rocks in Nevada a few years ago. One, about 42-inches long and 16 inches wide turned out to have a 34"x 12" crystal filling, mostly amethyst. Three were duds and one was cut in half before cutting it lengthwise. That rock was a geode, but not too impressive.
If you ever do cut your rattler open, I would be interested in knowing what caused the rattling.
 
  • #11
This is all great information. Thanks for everyone's help. My curiosity is almost enough to make me cut it open but having a rock that rattles isn't very common. It is the only one I have left so I think I will keep it whole.
 
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FAQ: What Are Rattling Rocks and How Are They Formed?

1. What is volcanic rock that rattles?

Volcanic rock that rattles, also known as tephra, is a type of rock that is ejected from a volcano during an eruption. It is characterized by its porous and lightweight nature, making it ideal for certain uses in construction and landscaping.

2. How is volcanic rock that rattles formed?

Volcanic rock that rattles is formed when magma, or molten rock, is ejected from a volcanic vent during an eruption. As the magma cools and solidifies, it forms small, lightweight particles that can be easily carried by wind or water. These particles then settle and accumulate, forming layers of tephra.

3. What causes volcanic rock that rattles to make a rattling sound?

The rattling sound of volcanic rock is caused by the air pockets or voids within the rock. When the rock is shaken or moved, these air pockets create a rattling noise. This is why volcanic rock that rattles is also known as "rattlestone."

4. Where can volcanic rock that rattles be found?

Volcanic rock that rattles can be found near active or dormant volcanoes, as well as in areas with a history of volcanic activity. Some examples of locations with abundant volcanic rock that rattles include Hawaii, Iceland, and the Pacific Northwest region of the United States.

5. What are the uses of volcanic rock that rattles?

Volcanic rock that rattles has several practical uses, including as a lightweight aggregate in concrete, as a filter media for water and air purification, and as a decorative element in landscaping. It is also used in the production of lightweight building materials, such as bricks and blocks.

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