Granite Countertops Are Magnetic. Who Knew ?

[Dwight_Frye]

I accidentally broke my old magnetic stud sensor which I always use in conjunction with an electronic type. I went down to the local True Value and picked up a new one made by C.H. Hanson which uses the rare earth/neodymium magnets. I like this one as it has a small bubble level built in which can be rotated 90 or 180 degrees.

The magnets are really strong, no problem at all zeroing in on nail heads in drywall and sticking right to them on the wall surface. But what surprised me was setting it down on a granite countertop in the kitchen and bathroom the magnets were attracted to the granite. Not as strong as sticking it to the side of a refrigerator for example but definitely magnetic across the entire surface of the countertops which are set down on plywood tops of the cabinet structures. Odd....

 

[Lyman]

Real granite sometimes has a little iron in it.

 

[JGmazda]

Iron in the Granite? Wow... Never knew that. Interesting find.

 

[LoneRanger]

This may explain why the LTE signal strength on my phone drops slightly when laying the phone flat on the granite counter top. The weak magnetic field may be effecting the antenna.

 

[Kestas]

It's probably magnetite, Fe3O4.

 

[Fawteen]

Who knew? It's not that much of a mystery. It's usually the dark portions of the granite (or gneiss or gabbro more likely) that contain inclusions of magnetic materials in trace amounts. It's pretty normal.

And I suspect you also may not know that most stone countertops that are called granite are actually not granite, but rather gneiss or gabbro. They all get lumped together as granite, but they really are not true granite.

 

[earlyre]

Some granites are naturally radioactive. They naturally contain uranium and/ or thorium.
As they decay they do give off radon and other natural decay byproducts, but in VERY minuscule amounts

 

[Driz]

Every single load of crushed stone I ever saw coming across our border crossings set off the radiation alarms. Every one and some other stone as well. That's why it's a good idea to check your basement for radon gas content. Poor ventilation and long term exposure can kill you from lung cancer.

 

[LoneRanger]

House we bought December last yr has black granite counter tops, or maybe the other types of stone mentioned above, as a layman I'm not sure. Anyhow, interesting info about the radon gas. I actually have a radon gas detector/monitor, about the only one made that's accurate. I need to set it up in the new house, had it setup in former house, it would vary usually showed as low as 1.9 to as high as 3.something. It was setup to trigger an alert tone if short term exceeded 4.0. You could switch it between short term mode and long term.

This is the one we have: