haematite can come from central/south america i believe...

I believe that hematite is mildly magnetic. And I recall hearing that with the magnetic hematite "fad" that people/Companies were using strong magnets to make the synthetic hematite magnetic- though I always doubted this claim. Found two sources that could be helpful.

Artificial Magnetic hematite is evidently NOT real hematite- but may be in fact a barium-strontium ferrite magnet (AKA ferrite) that has the magnetoplumbite structure instead. MinDat.org: https://www.mindat.org/min-35948.html

Is magnetizing hematite possible? Dept.of Physics, Univ. of Illinois: https://van.physics.illinois.edu/qa/listing.php?id=357&t=hematite-magnets

Though hematite is a first choice for the appearance of shiny black material in your pendant from Mexico, Obsidian, a volcanic glass, is also black and shiny, and can be magnetic as well, depending on source location. North American Archaeologist Journal: https://journals.sagepub.com/doi/abs/10.2190/QG75-MVKT-HE33-5VAQ?journalCode=naaa

Hope this helps,
Anne

Many years ago an archaeologist working in Mexico uncovered a large cache of magnetic hematite beads (or perforated objects) at a prehistoric site. She contacted me via Pete Francis. I responded that I thought they were not likely ornaments due to their excessive weight and probably had another use. She thought they were. Unfortunately, these objects were never published to my knowledge, and I had long forgotten about them until this posting jogged my memory.

Magnetite fits the criteria.

great add- sure- magnetite alone without the mix of pyrite one often sees in "healing" pendants is a good guess. I checked and there are polished cabochons of just magnetite AKA lodestone that are being sold for their so called "healing properties" that do resemble OP's example.

I appreciate all the information everyone has shared, thank you so much!

About obsidian, it's essentially glass, can glass be magnetic??

And a funny follow-up. Today I visited one of my favorite antique stores, and found a display of beaded necklaces. I went to pull one off and had to take several others off to get to the one I wanted, with a sales person helping me, and all the sudden all the necklace is stuck together! I realize there was a Blackstone bracelet right below all the necklaces, and as they came off they all got stuck to the same kind of black magnetic stone! It took us a few minutes to untangle them all.

I didn't think Obsidian, which IS glass could be magnetic, but as I read SOME can be, depending on Location found. Weird, right?!

Apparently, it can have iron particles in it, or other magnetic particles. I had no idea!

first, thank you to all who responded, all the information was very interesting.

now I'm really puzzled. I thought obsidian was basically volcanic glass. Can glass be magnetic?? So cool!

Today I visited one of my favorite antique stores, and found a necklace on a rack that I wanted to buy.. When I tried to take it off the rack to look at it more closely, suddenly all the necklaces next to it got tangled up together with mine. A salesperson was helping me, and we couldn't figure out what was going on until we realized all the necklaces were stuck to a bracelet (underneath the rack) with black stones in it that was magnetic!

Must have been the same material. Maybe I'll go back and take another look at it.