What Are Rattling Rocks and How Are They Formed?

[Bryon Palmer]

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?

 

[Greg Bernhardt]

Are you going to crack it open? :)

 

[Bryon Palmer]

Are you going to crack it open? :)

I would rather not.

 

[Evo]

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.

 

[jim mcnamara]

Looks like it could be pumicite - if it floats in water it probably is.

 

[Bryon Palmer]

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.

 

[davenn]

Hi you Bryon
welcome to PF

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

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

 

[Bryon Palmer]

Hi you Bryon
welcome to PF

"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!

 

[OmCheeto]

Sounds like a hollow version of our state rock: Thunderegg

Of course, without opening it, you'll never know.

 

[CapnGranite]

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.

 

[Bryon Palmer]

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.

 

[cosmik debris]

Rattling rocks are reasonable common here. There is a stream in the Waitaki valley where they are plentiful and a bit of a tourist attraction. I always presumed they were of volcanic origin.

http://www.newzealand.com/in/article/fascinating-fossils-and-rattling-rocks-in-waitaki/

 

[davenn]

Rattling rocks are reasonable common here. There is a stream in the Waitaki valley where they are plentiful and a bit of a tourist attraction. I always presumed they were of volcanic origin.

http://www.newzealand.com/in/article/fascinating-fossils-and-rattling-rocks-in-waitaki/

yes, that is one of the places we have done hunts for them :) and further north around the base of Mt Hutt etc