I suspect it is a lump of schist, the reflective bits being mica, perhaps a white mica like muscovite.
I see the shape is a bit like an arrow head, but I think that is coincidental (and a bit large).
The lighting and background is good, but the photos are too compressed to show the features we need to see. Please can you take some more, at high quality & resolution. Then we might be able to be more confident.
Also, if you know where the stone came from it might help.
This confirms it is a lump of mica schist.
Read more here, eg. - http://en.wikipedia.org/wiki/Schist
Mica usually occurs as quite small flakes (it is a platy mineral), but it can be found as quite large pieces - several centimetres across. These larger pieces were used as insulators in early electrical devices, but were partly superceded by artificial materials such as the original Formica (it was used 'for mica'). The more familiar decorative laminate 'Formica' came a bit later.