While perusing science daily, I stumbled upon this little release about early life and molybdenum.
All this talk of molybdenum led me on a quick stroll down memory lane. My undergrad was completed in the same department as the AIRIE group. They were working on developing the Re-Os chronometer for use with molybdenite.
One of the benefits of using molybdenite for geochronolgy is that Re is readily taken into the crystalline structure of molybdenite (Stein et al. point out it is commonly in the high ppm range!). At the same time, Os is excluded from the crystalline structure. This makes it easy to compare the parent and the daughter product.
This paper also points out the possibility that the amount of Re present in the molybdenite is directly related to the genetic conditions of the molybdenite formation. While they don't go into much detail on this, I would be interested in finding out more about this aspect.
I'm not much of an igneous or metamorphic person, but I found this paper a fun read anyway.
H. J Stein, R. J Markey, J. W Morgan, J. L Hannah, A Scherstén (2001) The remarkable Re-Os chronometer in molybdenite: how and why it works
Terra Nova 13 (6) , 479–486 doi:10.1046/j.1365-3121.2001.00395.x