Flint(?) Concretion

Terri

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This concretion is about 3cm. in diameter, it really looks like flint to me, I'm sure I could be wrong and I think I may be be seeing conchoidial fractures. The concretion formed around a nucleus that appears to have some structure, wether it's a fossil or not I don't know. :roll: I really expected the outside of concretion to sizzle, but it didn't, neither did the black flinty looking stuff nor did the nucleus. Any insight appreciated! :smile:
 

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Is that as round as it looks in the picture? I have seen lots of rounded rock but not rocks that are round so it really stands out. Could be something man shaped as a weapon?
 
Yes, it's my understanding that concretions can be perfectly round. I've had this for years and just enjoyed it but my curiousity got the better of me and I decided to crack it. I wasn't expecting to see the flintlike material or such a cool nucleus (possibly fossil?). Hopefully Kevin will clear things up. :cool2:
 
:oops: I went round and round (pun intended) :heee: on wether to call this a concretion or a nodule. What I read was that concretions always form around a nucleus, and when I searched nodules they were mostly oddly shaped formations. So I'm incorrect? :confused:
 
Kevin,
Can you explain the difference in what you would see between a geode and a nodule. I read the Wickipedia distinction but it was not clear how you would visually determine if the core was coated or formed as part of the rock (correct this undersanding of the differences if my paraphrase does not properly match the concept :oops:). Include in your tutoring how you would determine that this is not a geode please :sagrin:
 
I'm finding what seems to be a lot of contradictory information on nodule vs, concretion. I thought I had it penned down to concretion, but I will gladly concede to Kevins superior knowledge. :razz:
 
DWhatley;187930 said:
Kevin,
Can you explain the difference in what you would see between a geode and a nodule :sagrin:

A geode is hollow with crystals growing inside. A geode is a nodule that is hollow. :heee:

Terri;187931 said:
I'm finding what seems to be a lot of contradictory information on nodule vs, concretion. I thought I had it penned down to concretion, but I will gladly concede to ... :razz:


The best explanation is found HERE
Also see Siderite and Phosphate concretions/nodules.

To me, generally, concretions are large and soft(er) and nodules are small and hard. :sly:
 
Well, after reading the great link you supplied, of course you would be correct, chemically speaking. Technically, I should have called it chert. I read this article and based the decision to call the material flint on color and texture instead of chemical makeup. The Quartz Page: Flint and Chert

So, the differences in cryptocrystalline quartz, chalcedony, chert and flint would be crystal size and specific gravity and are nearly identical in chemical makeup to that of pure quartz. :cool2:

Thanks again Kevin!
 

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