I call this the ultimate (but covert) pick-up shirt of all time, simply because it is. All us regular non-mineralogists won't get what this shirt is saying, but those of you who are into memes (and are a slightly bit more resourceful) will.
I probably spoiled it already with the title, but if you still didn't get it, then read on.
But I'm going to be nice and let you in on the joke. First off, let's start with a quick and simple lesson in mineralogy. Actually, we're only going to be looking at one mineral: (Mg,Fe)7Si8O22(OH)2, which is the one on the shirt. That's actually the chemical formula for cummingtonite.
Gents and gents, I kid you not. In case you didn't get it or the significant of cummingtonite (I just had to say it again), then read the entire second paragraph again.