Very interesting find, thanks for posting. My curiosity was piqued and I had to learn more. I found an in depth article at Science Alert found at this link:
http://www.sciencealert.com/hypatia-stone-extraterrestrial-meteorite-composition-like-nothing-in-the-solar-system

To summarize, these pebbles do not match the mineral composition of any known meteorite. They possibly originate from the Oort belt at the edge of our solar system. The most likely source is the nucleus of a comet.

What I find most surprising is the presence of nickel without iron (this is a given with any terrestrial rocks and meteorites) and diamonds in a carbonaceous matrix. Diamonds form under extreme pressures, which is not surprising on its own. However, the authors suggest the rocks formed in very cold conditions. That could be why they suspect the rocks originate from the center of a comet.

That’s quite the mystery! Thanks for sharing.