My grandparents found a rock at the beach that spontaneously combusted. what is it?

my grandparents were out walking the dog before sunrise, and noticed an odd rock which felt warm, they left it, it was sitting at the shore line, not fizzling or bubbling, it was low tide,so it must have been submerged at one point within the last 4 hours.
Later on their way back, the sun had rose and the rock was now fizzling , when they touched it with their sandal, it burst like a waterballoon of petrol and created a bright thick fire like an oil fire, as if the golf ball sized stone was filled with super heated napalm.

My grandparents kicked the small stone which had not melted, into the water and it made a huge explosion which intensified the flames, as if it were sodium.

My grandppa kept the stone after it had been burning in the shores wash line for an hour, and took it home. when he got home, he put it into a glass of water and it violently fizzled and sustained a flame momentarily.

i checked the so called stone, and it looked like a standard beach pepbble with a tiny bit of quartz attached.

What could it have been? that would have passivated in the water and not completely reacted until the inert skin was broken. my grandparents claim it was the sunlight that triggered the exothermic reaction.

Anyway, they say the flames werent blidingly bright which possibly rules out alkali metals, plus it was yello which rules out lithium ontop of the meals, as well as the fact that it had previously been under water.
does anyone know what it is? like i siad, it looks like standard smoothed beach rock now, its exterior was what burnt.

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aeray5 years ago
Here is a link to a recent, possibly related, case.
iceng aeray5 years ago
That's a scary condition...
aeray iceng5 years ago
oldmanbeefjerky (author) 4 years ago
i think i discovered what it was!
A chunk of metalic phosphorus, ive looked into it deeper, and sometimes phosphuros in artilary shells can form a tough oxidized coating that will protect it, from water, and also keep it afloat.
however, being pure oxide, it is alkaline and eventually disolves into water, forming hydroxide and such. as it does this it flakes off. anyway, im 100% certain this is it.
Re-design5 years ago
Isn't this the same story that came up about 6 months ago???
oldmanbeefjerky (author)  Re-design5 years ago
what story? can you show me a link to this story?
No, Phobo-Grunt wasn't even launched then. Pffff
iceng5 years ago
Could be a common enough deep ocean methane ice rolled under and encapsulated by sediment forming a rocky substance causing pressure
pyro emissions once the rock enclosure is sun heat activated.

A
methainICE.jpg
oldmanbeefjerky (author)  iceng5 years ago
your positive it could have been ignited from the sun?
That might explain some things, but not the reason why it continued to bubble in water when my grandfather got home and put it into a glass of water, unless of course the pebble the ice was frozen around, was soaked into the pebble, and slowly comming out of the stone?

liquid methane could have formed too right? that would explain the liquid combusting, but not why it intensified in the water, unless of course it acts like dry ice and melts quicker in water because it would have been a higher temp.

im going to do some more research on this methane ice, and intil i can confirm it, this seems the most plausible idea yet.

EVERYONE ELSE I MEAN THIS IN TOTAL SERIOUSNESS OK, AND IDE LIKE SERIOUS PLAUSIBLE RESPONSES THANKYOU!
rickharris5 years ago
It was.. It was... Aggggh!..............
Its Sontaran technology, you'll die if you use it.
You guys really shouldn't leave that kind of stuff lying around.
Yea, it generally doesn't end well.
Thermionic5 years ago
I think it was an automagic transformer egg.
lizzyastro5 years ago
It *was* a phoenix egg, but by kicking it into the sea you have drowned the poor little chick :-(
Jayefuu5 years ago
It's definitely a piece of Phobos-Grunt. Don't let them have it back!