Is this a petrified fruit or a concretion?

[Jimm2]

I found a 2 inch diameter round rock in Oregon. When I hit it with a hammer it split it in half and there was a "seed" in the middle that had the appearance of an apple seed in shape, color, and size. I know that concretions start with a seed, but the inside pattern is not like any concretion I have seen. I goes out in "rays" from the center like a citrus fruit. What do you think it is? I sanded one of the halves.

 

[Bystander]

Gypsum.

 

[Jimm2]

No. I have seen "desert roses" (gypsum). None ever formed like this. But if you do find a photo of one that has rays perfectly formed around a center point, I would like to see it (contained within a sphere).

 

[Bystander]

 

[Andy Resnick]

Interesting... almost looks like an avocado pit.

 

[jim mcnamara]

Okay - instead of bumbling about let's try Science:
1. do you know how to test approximate Moh's hardness? Give us a number.

2. Does the rock fizz or bubble or become shiny clean under the drop when you put a tiny drop of acid on it? Lemon juice will work.

Since you cut it, therefore it must be fairly soft - which is why I asked #2.

 

[Jimm2]

I tried two different acids and it did not fizz. Neither a fingernail nor a penny scratched it. So I guess that rules out gypsum.

 

[Jimm2]

I did not cut the rock. I hit it with a hammer until it split in two. I did not sand the outside. It is a hard rock.

 

[jim mcnamara]

How about the other two tests?

 

[Jimm2]

It seems to leave a shiny trail of metal when I try to scratch it with a paper clip. With my bifocals I just couldn't focus that well even with magnifying glass to see if it left a permanent scratch. If it did it wasn't a deep scratch. It does not scratch glass.

 

[OmCheeto]

Interesting... almost looks like an avocado pit.

I've never cut open an avocado pit, so I wouldn't know.
It looks like a petrified Osage Orange fruit to me.

Maybe polished in a river bed.

Could also be one of those round tree thingys. (google google google).. Burl!
Though I'm not a wood burl expert.

Where's @phinds when you need him.

 

[jim mcnamara]

Burls generally are the result of a virus infection in trees - like Witches broom for example. They do not look like that in general. Basically the plant tissues are all 'screwed around'. Burls are probably best thought of as growing a tumor on a tree. Some are bacterially induced.

Structurally it does resemble osage orange (Maclura pomifera) fruits, yup. And a distribution map shows that it is native to Oregon
http://plants.usda.gov/core/profile?symbol=MAPO

So, if the concretion is more than about 2-3 inches in diameter Osage orange looks like a very possible source. The fact that it split so conveniently with a hammer also indicates the fruit structure (locules) that M. pomifera has. As a comment, whacking things like that with a hammer is a great way to create a pile of dust and pebbles, most times. You lucked out as they say.

The only issue is formation. It's Moh's hardness is high-ish, and it clearly is not a carbonate. So, I'm not sure what mineral it is.

However that is a nice specimen. If you know a rockhound or there is a local rock shop, consider finding out about getting the two inside surfaces of the ball polished. You know, all shiny. Something like that may have some real collector value.

 

[zoobyshoe]

However that is a nice specimen. If you know a rockhound or there is a local rock shop, consider finding out about getting the two inside surfaces of the ball polished. You know, all shiny. Something like that may have some real collector value.

I wouldn't do anything to it until it's positively identified one way or the other. The still rough side shows the direction of the "flakes" or whatever they are much better than the sanded side, and I'd assume that would help with identification.

If it were an orange, it would be very peculiar for it to have petrified without first having dried up into a shape not immediately recognizable as an orange. Seems more likely it would have been a seed or nut of some kind, something that started out with more oil content than water, so that when it dried out, the overall shape was not much distorted.

Were I the OP I would email images to whatever paleobotanists I could find the email's of. They might already know what nut or fruit it is, or might already know of some purely mineral process that has this organic-looking result.

 

[256bits]

Kinda looks like this aso,

If it is pyrite or marcasite (which I am not saying it is ) degradation with moisture could have made the specimen more flaky.
https://en.wikipedia.org/wiki/Marcasite
In any case, mineral deposits can look like organic material petrified.

 

[256bits]

The outer yellow can be limonite, which can be lemony yellow in color, or darker.
https://en.wikipedia.org/wiki/Limonite

 

[ProfuselyQuarky]

If it is pyrite or marcasite (which I am not saying it is )

aah . . . iron pyrite (otherwise known as fool's gold!)

 

[dipole]

you should have someone who knows what they are doing take a look at it before you ruin it more than you already may have.