Elementary physics: Why do some objects acquire magnetic fields...

Factual Questions
1

…absent any obvious exposure to existing permanent magnets or magnetic fields?

For example, I have this square glass container with a metal lining on the bottom, in which I keep mainly coins, guitar picks, and other objects. Some are metal and some aren’t.

Picture
(You may need to rotate it a quarter-turn to the right.)

Originally this object was a decorative candle which, when used for its original purpose, would have been placed on a table upside down with respect to this shot. I’m not sure what kind of metal that is, but it’s obviously become highly magnetic. Notice that the penknife sticks not to the container itself, but to a steel screw which, in turn, sticks to the container. To remove these objects requires a significant tug, by no means is it the case that they’re barely hanging on.

I usually have this in my medicine cabinet whose shelves are just wide enough hold it, the idea being that when getting ready to to go out I can grab a few coins if I think I’ll need to feed a meter or tip a barista. I only mention the medicine cabinet because that’s obviously metal as well.

I’ve also noticed that herb grinders become magnetic, especially at the center of rotation.

What gives? I know that under certain conditions a piece of metal can be imbued with a permanent magnetic field by being rubbed or struck a certain way with another metal object, and that will happen with the herb grinder, as the top part is twisted over the stationary base. But how did my glass and metal box become so strongly magnetized?

2

Earth’s magnetic field?

I just went and checked the knifes in my kitchen drawer, all of which are roughly alined in N/S direction. Most of them are slightly magnetic, and the sharpening steel will lift a four inch nail!

Also checked my cast-iron mortar and pestle, but nope.

3

It looks to me like there’s a magnet inside the container. Try emptying everything out of it.

ETA: That’s not to say that items can’t be magnetized by the Earth’s field. They can. But that looks like it has to be magnetized stronger than you’d be able to get from just the Earth’s field.

4

I have one of those glass candle holders exactly like in your picture. The metal lining is the top, not the bottom, and it has a magnet in it. You can buy refill candles that have a small metal insert in the bottom that fits over and attracts to the magnet to hold it in place. They’re made by Glade.

Here’s the best image I could find online. This one’s round.

5

It didn’t get that way by accident … it doesn’t happen that steel becomes magnetized by such “every day” domestic usage. You couldn’t even make a permanent magnet from these steel objects if you were trying … - permanent magnets are of a special composition.
Thats quite a strong magnet… it must be a rare earth magnet in the little lumpy bit.

6

False on all counts.

7

They have a relatively high mass (magnetic mass) compared to their surroundings?