The Old Ruminator
Well-known member
No its not a potato. Buried in sediment inside a cave. Andy F. will know.
P8110003 by Nicholas Chipchase, on Flickr
P8110003 by Nicholas Chipchase, on Flickr
Another Thing To Identify Please
- Thread starter The Old Ruminator
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Andy Farrant
Active member
It is most probably a chert nodule. If it is from East Mendip, you do get chert nodules in the limestone (particularly common in the upper part of the Black Rock Limestone), but as ever it is hard to tell from a photo, especially when caked in mud. The other possibility is an oncolite (an algal concretion akin to stromatolites) which do occur in the Clifton Down Limestone, but the morphology doesn't look right. Best to clean it and if it is very hard and siliceous, then it is chert.
The Old Ruminator
Well-known member
Thanks all. It came from Bleadon Cavern, West Mendip.
The Old Ruminator
Well-known member
A bit more from the finder.
It came from a filled mine shaft on Bleadon Hill in ocherous earth. It has been cleaned, a smaller similar one is CaCO3 - massive fizzing with HCl - and grey inside, not chert. I have a similar piece that has formed as a crust rather than a nodule. Don't want to break the poodle, but will hopefully find more tomorrow.
It came from a filled mine shaft on Bleadon Hill in ocherous earth. It has been cleaned, a smaller similar one is CaCO3 - massive fizzing with HCl - and grey inside, not chert. I have a similar piece that has formed as a crust rather than a nodule. Don't want to break the poodle, but will hopefully find more tomorrow.
Pitlamp
Well-known member
My attention's just been drawn to this by a friend; can I ask, is your specimen at all granular inside?
By this I mean could it be a calcite cemented sandstone?
(Or even calcite with some SiO2 [sand or silt] grains within it?)
Both would react well with HCl.
I ask because we found something similar in a cave in the Dales this summer. Just wondering if we could learn anything useful from you, if you've investigated further since the last post around three months ago. Thanks.
By this I mean could it be a calcite cemented sandstone?
(Or even calcite with some SiO2 [sand or silt] grains within it?)
Both would react well with HCl.
I ask because we found something similar in a cave in the Dales this summer. Just wondering if we could learn anything useful from you, if you've investigated further since the last post around three months ago. Thanks.
Pitlamp
Well-known member
Here's the one I was on about in my post above. It came out of a sump which now carries only percolation flow and the hemispherical blobs are composed of calcite cemented sandstone on the surface of the limestone block (i.e. they're not inclusions within the limestone itself). There are several other examples still in the sump in question.
Samples of these blobs have been sent to people who know a lot more about this sort of thing than I do but no consensus as to their origin has yet been arrived at. I'm told that no such thing is included in Art Palmer's book on cave minerals of the world (with thanks to the person who looked on my behalf).
Just wondering if any forum users might have useful suggestions - and whether there's any connection between these blobs and the item brought to our attention by The Old Ruminator above?
Samples of these blobs have been sent to people who know a lot more about this sort of thing than I do but no consensus as to their origin has yet been arrived at. I'm told that no such thing is included in Art Palmer's book on cave minerals of the world (with thanks to the person who looked on my behalf).
Just wondering if any forum users might have useful suggestions - and whether there's any connection between these blobs and the item brought to our attention by The Old Ruminator above?
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