Why did this strange grey rock beep with white mineral substance?

[kitt]

Sorry for bad pic my cam just died.
Went to the beach and got about 10 minutes in with my detector and this rock came up under 5cent icon on the ace 250.
I let it soak in some water and rinsed it off and now this is what it looks like. And it still beeps 5 cent under my detector.
I have Identified the mineral as priceite: calcium borate. The rock I still cant figure out why it beeps.

 

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[mohawkman4081]

It's a haunted skull rock!

 

[Back-of-the-boat]

Are you sure it is a rock and not a piece of melted aluminum there is a lot of melted aluminum at the beach. (Bonfires and beer cans= melted aluminum)

 

[DocBeav]

Or old lead, turns white with age.

 

[Msbeepbeep]

Detector said it's metal.

I had a weird item make mine beep, a large quahog (clam) I didn't cut it open, so to this day I have no idea why it set the detector off.

I've also pulled my probe out of the hole with a black shinny rock stuck to the end of it, magnet! First time I've ever had that happen.

This hobby is full of surprises!

 

[seychik]

How heavy is it, compared to a sinker. I would take a hammer to it to see if it crumbles or bends, although that would probably be the end of it.

 

[kitt]

Its really light in weight. Your not supposed to have fires at this beach but it does feel light and hard like aluminum. At a different beach I found these other 2 balls of aluminum. If its aluminum it might have been in the early 1900's, when the land there was owned during 1800s by some really rich guy. Could be why its almost black with age and the other 2 are not.
Other then that, the other 2 balls came up on a different icon.

 

[WHADIFIND]

As long as it doesn't sit there and beep all night, I'd just leave it alone.

 

[BigWaveDave]

There is a perfectly plausible scientific explanation, and you are not the first to experience this, fact is as time goes on, this will happen to us a lot in the future. Pull tabs have an unsteady molecular composition, which left undetected for an unknown number of years, they take on properties of rocks and clams. this will prove to be the end of the metal detecting hobby on the worlds beaches by the year 2025.