Any ideas what this is.

Must be 20yrs or so since I came across this while digging the allotment.
It appears to be metallic, not quite spherical but almost.

I seem to remember it being faintly attracted to a magnet so assumed it was iron.

Its fairly heavy for its size, heavier than a stone of the same size.

Anyway, its spent the last 20yrs in the greenhouse on the shelf.
A few weeks ago I noticed a white powder forming on it.
I'm guessing some kind of reaction/oxidization.

I picked it up today and it fell into two parts.
It's got me wondering what it is and how it was formed.
So any geologists out there?

 

Nice one Pete, its a Marcasite Nodule, FeS2. Same as iron pyrites but with a different crystal sytem ( Not Cubic)

They form usually in the chalk, around organic remains. They do oxidise unfortunately.

I had a lovely one size of a cricket ball from the cliff at Folkestone, it exploded about 20 years later

 

Wow...

 

Double wow

 

Triple wow

 

WOW, thanks for the info Ziggy.

So if it had been left in the soil it would not have exploded?
As I guess its been around a long time before I found it.

Its strange that it just suddenly decided it was going to split.
I'll have to use it for starting bonfires now.

 

No worries Pete

Bummer isn't it, quite happy for 90 million years & then just commits suicide

If I had realised, I would have sealed mine straight away.

They form in long shapes that would be more at home in "Private" shops too Still with the radiating crystal structure.

People used to think they were thunderbolts, but people used to think a lot of things.

 

Ahhh...so what i thought were thunderbolts are actually marcasite nodules....wait till i tell my friends they'll look at me as though i've got three heads

 

Cor,
I wish I was clever like you Brian Ziggy

 

You haven't?