Some little time ago now, I found what I believed to be a meteor, in a quarry, near Ringwood in Hampshire. I have attached an image of my find.
The total weight of the object is 590 grams, with the inner 'core' representing some 232 grams of that. The overall size is 12cm x 8cm x 7.5cm, with the inner core begin 9cm x 6 cm x 3.5cm.
If anyone could offer an opinion as to whether this might be a meteor, or not, I should really pleased to hear from you ?
I think it is an irontstone concretion or nodule.
Such things may occur somewhat in isolation or in iron ore-rich beds ('ironstone', as often used in local building - http://www.flickr.com/photos/meabbott/5926139482/).
'The geology of the country around Ringwoood' mentions ironstone and ferruginous concretions/nodules.
Here's a cross-section through an ironstone concretion, showing the concentric layers
- http://www.bradfordonavonmuseum.co.uk/archives/580 (scroll to the end of the page and click on the photo).
You can imagine from that how selective weathering could have produced the effect seen in your specimen.
You are not alone in wondering if, in spotting such a specimen, you have found a meteorite. Have a look at these other discussions
Other opinions appreciated...
I agree with Mike - it's an iron rich concretion - these are very common in my local cretaceous ferruginous sandstone.
They have these interesting layers but splitting them reveals nothing I'm afraid - nice iron oxide colours though.
Mike we found similar items in a sandstone ravine after a rain. Your response makes me ask this question: The stones we found were round ....some like eggs...and when out of curiosity we "cracked" some open there were concentric layers of a black almost tarry appearance and the inner hollow was filled with the finest sand I have ever seen.....I am attaching a couple of specimens for your observation. Are these the same ironstone concentrations to which you refer in your response?
We are in Erath County Texas. I also am curious about the purple color in the large unbroken one. Is that paleosole? we do have a layer that we discovered in a creek but it is at a much lower elevation than the area where the sandstone was found.
Yes - concretions.
1. Sandstone (and other sedimentary rocks) are composed of particles and cement. The cement arises post-deposition, by crystallization from fluids in the pores, and it is that which holds the rock together (though, there are other mechanisms that do the same thing).
2. Cementation is one of the processes that happens in the early stages of lithification. In this phase (diagensis), the physical conditions are changing from those pertaining when the sediment was deposited. As a result there are tendencies for the minerals making up the particles and/or cement to change their chemical and physical structure (striving to maintain equilibrium). Such changes may be evenly distributed through the evolving rock, or they may be exaccerbated here and there due to local anomalies. The latter can manifest itself as concretions.
3. Concretions are a little like rain drops, in that they may form spontaneously in clean air, or they may nucleate on an anomaly, such as dust or pollen in the case of rain. With concretions, it may be a fossil or an abnormal mineral grain that serves to get it started.
4. As the concretion grows, chemical changes are likely to be continuing, and not necessarily in a smooth way. That can account for the concentric banding in (some) concretions (as in the examples above).
5. Depending on the history of the sediment-rock, the concretion may eventually stop growing, becoming frozen in time, possibly to be found millions of years later when the rock is exposed after all sorts of geological events. If it is sufficiently disctinct from its host rock, it may become loose and separate.
6. Now it is subject to rather different physical conditions to when it was growing and while it was lithified. So further chemical and physical changes occur - looseley referred to as weathering.
With your concretion, I suspect:
1. Circumstances were such that it developed a concentric zoning as it developed, albeit with just two broad zones.
2. At some later stage, perhaps once exposed to modern weathering, the cement in the central zone may have dissolved, leaving just the original particles as the fine sand you observed.
3. (unrelated to the preceding explanation) The purplish coloured area may be due to chemical changes to the surface since the concretion was weathered out of the rock, or it may be other material precipitated on the conretion's surface. I do't think it is related to a palaeosol.
4. Dating. There is no particular way of dating concretions, ie. there are no evolutionary trees or broad stratigraphies as there are with fossils. To date a concretion, you would have to try the normal methods as for any rock: physical dating techniques and/or dating by implication through fossils in the same host rock. However, if the local stratigraphy is known, concretions may occur in particular beds or horizons, and biostratigraphically dated strata above or below may enable the concretions to be dated as being within that range.
I see the logic in your tagging your question to the end of the preceding one.
But in future if you could start a new question, that would help to keep questions from getting muddled, and it keeps them from getting too long.
In any question, by all means refer to a pre-existing one by using its URL copied from your browser's address bar.
These are my opinions; I cannot claim them as facts.
Hope that helps.
Keep up the enthusiasm!