d6 is the damage die.
on a slightly seperated note, I believe it is like dire weapons where it can be used as a double attack in a round with the usual penalties for two weapon attacks.
It can also be made of dark wood.
here are some links for yo to verify my claims:
basic weapon info
http://www.d20pfsrd.com/equipment---final/weapons/weapon-descriptions/quarterstaff
double weapon:
http://www.d20pfsrd.com/equipment---final/weapons#wpn-quality-double
Darkwood:
http://www.d20pfsrd.com/equipment---final/special-materials#TOC-Darkwood
is that enough information, or is it too much information?
