RockHoundLounge Forum - Concretions, Geofacts & Other Confusing Creations

RockHoundLounge Forum › Mineral Photography / Collections › Fossils › Concretions, Geofacts & Other Confusing Creations

‹ Previous Topic | Next Topic ›

Pages: 1

Concretions, Geofacts & Other Confusing Creations (Read 5196 times)

JoeM God Member Offline I Love YaBB 2.5 AE! Posts: 4204 Location: Wake County, NC Joined: Sep 30^th, 2010 Gender:	Concretions, Geofacts & Other Confusing Creations Feb 4^th, 2021 at 7:59pm	Print Post
	I love Pokes' 'Fossilized Plum" post below and it inspired me to start this thread. There are so many rocks we find where we say, "It's Got to be a ....!" Poke's Plum is more of a naturally water worn rounded granite cobble, a "Geoform'? Concretions are a great study, and are always making us wonder. Here's a link to a good article about concretions and how they can fool us. https://archaeology.uiowa.edu/natural-objects-masquerade-cultural-artifacts Here are some pictures of an iron oxide concretion like the one in the above article. It kind of looks like half a plum or peach? I wanted to show all sides so lots of pics.

	DSCN9226.JPG ( 210 KB \| 73 Downloads ) DSCN9228.JPG ( 217 KB \| 68 Downloads ) DSCN9230.JPG ( 206 KB \| 67 Downloads ) DSCN9232.JPG ( 223 KB \| 70 Downloads ) DSCN9236.JPG ( 212 KB \| 67 Downloads ) DSCN9240.JPG ( 194 KB \| 68 Downloads )
	IP Logged

JoeM God Member Offline I Love YaBB 2.5 AE! Posts: 4204 Location: Wake County, NC Joined: Sep 30^th, 2010 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #1 - Feb 4^th, 2021 at 8:01pm	Print Post
	What's this?

	DSCN9256.JPG ( 203 KB \| 69 Downloads ) DSCN9263.JPG ( 213 KB \| 71 Downloads ) DSCN9243.JPG ( 220 KB \| 65 Downloads ) DSCN9246.JPG ( 202 KB \| 68 Downloads ) DSCN9249.JPG ( 181 KB \| 67 Downloads ) DSCN9254.JPG ( 210 KB \| 66 Downloads )
	IP Logged

JoeM God Member Offline I Love YaBB 2.5 AE! Posts: 4204 Location: Wake County, NC Joined: Sep 30^th, 2010 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #2 - Feb 4^th, 2021 at 8:19pm	Print Post
	Concretions can form from a lot of different minerals. Iron oxide concretions are found in many places and there's limestone, calcium carbonate, silica, like chert and flint concretions. (Technically, not all hollow voids filled by silica like chert and flint would be called concretions.) But this piece of English flint is definitely #1 in my collection.

	DSCN9546.JPG ( 215 KB \| 64 Downloads ) DSCN9536.JPG ( 226 KB \| 65 Downloads ) DSCN9538.JPG ( 226 KB \| 68 Downloads ) DSCN9540.JPG ( 195 KB \| 65 Downloads )
	IP Logged

JoeM God Member Offline I Love YaBB 2.5 AE! Posts: 4204 Location: Wake County, NC Joined: Sep 30^th, 2010 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #3 - Feb 4^th, 2021 at 8:34pm	Print Post
	Here's another good link on all kinds of concretions. http://brovey.yolasite.com/resources/Concretions.pdf And Wikilinks is pretty good, https://en.wikipedia.org/wiki/Concretion And here's a piece of fine sandstone and clay I wonder about. I guess I'm going to have to polish the bottom now just to check for any formation, but all I can see with a loupe is sandstone. Sure looks like the end of a humerus or something.

	DSCN9269.JPG ( 218 KB \| 65 Downloads ) DSCN9272.JPG ( 250 KB \| 74 Downloads ) DSCN9278.JPG ( 206 KB \| 68 Downloads ) DSCN9282.JPG ( 224 KB \| 70 Downloads )
	IP Logged

JoeM God Member Offline I Love YaBB 2.5 AE! Posts: 4204 Location: Wake County, NC Joined: Sep 30^th, 2010 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #4 - Feb 4^th, 2021 at 8:50pm	Print Post
	ROCKS! Now if anyone has any comments about any of these specimens, or have some of your own, please feel free to post them here. I don't know about this one either. It looks like a fossilized bi-valve shell but I'm not sure what the rock is? Probably some sort of quartz. It looks like hardened clay but the hardness on the broken end is about 6 and it does not fizz with vinegar. I haven't tried anything stronger. I wonder if it is a fossil or a Geofact. A section of layers that washed out and was rounded? First 4 pics dry, last 4 wet.

	DSCN9137.JPG ( 199 KB \| 70 Downloads ) DSCN9140.JPG ( 191 KB \| 70 Downloads ) DSCN9145.JPG ( 215 KB \| 68 Downloads ) DSCN9147.JPG ( 255 KB \| 74 Downloads ) DSCN9151.JPG ( 156 KB \| 71 Downloads ) DSCN9154.JPG ( 198 KB \| 72 Downloads ) DSCN9157.JPG ( 167 KB \| 69 Downloads ) DSCN9159.JPG ( 172 KB \| 69 Downloads )
	IP Logged

daves64 Senior Member Offline Rockaholic Posts: 456 Location: Ellensburg WA Joined: Jun 27^th, 2018 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #5 - Feb 5^th, 2021 at 1:26am	Print Post
	Your first one looks like part of a really "hard" core guacamole. As for the others.. not sure.

	avocado_1050x700.jpg ( 40 KB \| 72 Downloads )
	IP Logged

JoeM God Member Offline I Love YaBB 2.5 AE! Posts: 4204 Location: Wake County, NC Joined: Sep 30^th, 2010 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #6 - Feb 6^th, 2021 at 11:24am	Print Post
	What a pretty avacado. And the pit fits!


	IP Logged

CBDuke Junior Member Offline RockHoundLounger Posts: 96 Location: Baltimore Maryland Joined: Feb 22^nd, 2020 Gender:	Re: Concretions, Geofacts & Other Confusing Creations Reply #7 - Apr 6^th, 2021 at 10:19pm	Print Post
	Concretions are a feature of a lot of formations. Here in the east we find them associated with devonian, ordavitian and Permian deposits. They are always dark grey and hard as anything . One site near Cacapon Bridge WV. There are usually pieces or whole fossils incorporated into the concretions. They are formed by large amounts of amorphous silica being dumped into still water. During these geological periods the strato volcano that is South Mountain was erupting almost continuously. Volcanic ashe is a terrific source for amorphous .silica. Warning ;donot attempt to break large concretions with a small rock hammer . They are insanely hard.


	IP Logged

Pages: 1

‹ Previous Topic | Next Topic ›