I would have guessed that it was some sort of artifact, but according to the discussion thread at the whatsthisrock subreddit, it is fossiliferous limestone (tumbled smooth by the river).
Geologist here - Looks like you have a fantastic piece of Packstone / Biomicrite. Without being able to run the tests on it, the matrix (blue) is probably a calcareous mudstone, with the blue colour being formed from trace minerals in its composition. Like others have said, the white parts are cross sections of shells, and in this case they look like bivalves.
Very, very cool. If I were at that river I would fill my pockets with these.
More on fossiliferous limestone (which does not typically have a blue matrix).
I'm seriously thinking about a trip to Italy but I've got to check the rules first.
ReplyDeleteIf you get some, let me (us) know. Seriously.
ReplyDeletePainfully beautiful. Much more attractive than a diamond to me.
ReplyDeleteI found an example of fossiliferous limestone having been crafted into a snuff bottle:
ReplyDeletehttps://www.ebay.com/itm/186662511751?_skw=%22fossiliferous+limestone%22&itmmeta=01JEFQF3GC448TKEPJA92AZ020&hash=item2b75f3e487
Also checked Google Images and Google Shopping. Lots of fossiliferous specimens on the world marketplace, but none with the blue matrix shown above.
DeleteI've checked around on fossil material from that area and my suspicion is the blue color is mostly due to having been in the water for an extended period and is only surface deep.
DeleteI think if you tried to polish it it would wind up white on black. Still extremely attractive but not quite that nice blue.
Interesting (and makes sense). Thanks.
Deleteswoon! wow!
ReplyDeleteoften found on shores of Lake Michigan. Petoskey stones are a variety.
ReplyDeleteWhat in the fresh water would make it blue?
ReplyDeletexoxoxoBruce
I can think of two possibilities One would be some sort of mineral present in that area, I think it's pretty unlikely because I believe the real matrix is black and thus would be difficult to stain. The way I think it probably happened is bleaching/washing out just due to the water and it's probably only skin deep.
DeleteTrace amounts of both copper and zinc can result in blue colors in mud. Benitoite is a barium-rich mud which is valuable as a semi precious gemstone.
ReplyDelete