Boninite!

Well, if you're thinking the difference between "bone-in" and "boneless", that's not right. This is an "-ite", i.e., a mineral (actually, well, a rock) -- it's an igneous rock. Here's what Wikipedia has to say about it:

Boninite

Two key things here:

"The rock is named for its occurrence in the Izu-Bonin arc south of Japan", and

"Boninite is considered to be a primitive andesite derived from melting of metasomatised mantle."

So while there are lots of other kinds of "-ites" found erupting from volcanoes modernly, boninite has never been found erupting -- until now. The remarkable underwater eruption footage of the West Mata underwater volcano near Tonga was accompanied by sampling -- and it turns out that West Mata is erupting boninite!

And that's really interesting because it's never been seen before.

OK, that's cool, and I've beaten Klemetti to it.