Thread by @mikamckinnon

Today’s #MinCup2019 is a face off between Very Interesting Properties.

https://twitter.com/mineralcup/status/1170621210507587584

Lots of minerals have neat optical effects, but #Ulexite is a bit different.

Light doesn’t pass straight through, like with #quartz or #halite (salt), nor does it have the birefringence of #calcite. Instead it’s a mineral of natural fibre optic channels transmitting light.

#Ulexite grows as a bundle of fibers, each of which totally internally reflects light. It’s the same basic optics behind why diamond is sparkly.

https://twitter.com/mikamckinnon/status/1109917147277467648

(This is when I realize I have NO IDEA where I put my lasers when reorganizing my office last summer. Whoops.)

Meanwhile #magnetite is magnetic. Like REALLY magnetic. Like “Who needs iron filings when you can go to the beach with a magnet to collect magnetite sand?” magnetic.

Which means you can use it to visualize magnetic field lines. Ooooooh, pretty!

& #magnetite helps tell a big, huge paleoclimate story.

(Yes, any time anyone asks about my banded iron formation jewelry, I tell the story of stromatolites.)

https://twitter.com/mikamckinnon/status/1039601500794675200

Vote either way. Both are Extremely Good Minerals That are super-fun to play with.